text:
UploadSign inJoinBooksAudiobooksComicsSheet MusicEditors' Picks BooksHand-picked favorites from our editorsEditors' Picks AudiobooksHand-picked favorites from our editorsEditors' Picks ComicsHand-picked favorites from our editorsEditors' Picks Sheet MusicHand-picked favorites from our editorsTop BooksWhat's trending, bestsellers, award-winners & moreTop AudiobooksWhat's trending, bestsellers, award-winners & moreTop ComicsWhat's trending, bestsellers, award-winners & moreTop Sheet MusicWhat's trending, bestsellers, award-winners & moreCategoriesArts & IdeasBiography & MemoirBusiness & LeadershipChildren'sComputers & TechnologyCooking & FoodCrafts & HobbiesFantasyFiction & LiteratureHappiness & Self-HelpHealth & WellnessHistoryHome & GardenHumorLGBTMystery, Thriller & CrimePolitics & EconomyReferenceReligionRomanceScience & NatureScience FictionSociety & CultureSports & AdventureTravelYoung AdultCategoriesArts & IdeasBiography & MemoirBusiness & LeadershipChildren'sComputers & TechnologyCooking & FoodFantasyFiction & LiteratureHappiness & Self-HelpHealth & WellnessHistoryHome & GardenHumorLGBTMystery, Thriller & CrimePolitics & EconomyReferenceReligionRomanceScience & NatureScience FictionSociety & CultureSports & AdventureTravelYoung AdultCategoriesAdaptationsChildren’sCrime & MysteryFictionHumorMangaNonfictionRomanceSciFi, Fantasy & HorrorSuperheroesYoung AdultPublishersArcanaArchie ComicsBOOM! StudiosDynamiteIDW PublishingKingstone ComicsMarvel ComicsSpace Goat ProductionsTop Cow ComicsValiant ComicsZenescopeDifficultyBeginnerIntermediateAdvancedMixedInstrumentBrassDrums & PercussionGuitar, Bass, and FrettedPianoStringsVocalWoodwindsGenreClassicalCountryFolkJazz & BluesMovies & MusicalsPop & RockReligious & HolidayStandardsWelcome to Scribd! Start your free trial and access books, documents and more.Find out moreINTERIOR LIGHTING DESIGN A STUDENT'S GUIDEKevin Kelly M.A. B.Sc.(Eng) C.Eng. MCIBSE. MIEI. Kevin O'Connell M.A. B.Sc.(Eng) C.Eng. MCIBSE. MIEI.
COLOUR RENDERING (of a light source) The ability of the source to render colours accurately. the CCT of a white fluorescent lamp is 3500 K.
Interior Lighting Design . CHROMATIC ADAPTATION The eye adapting to changes in the colour of light sources. “Good colour rendering” suggests the source is rendering colours similar to the way daylight would. APPARENT COLOUR The subjective hue of a source. The apostilb is not an SI unit and is equivalent to one lumen per square metre. Ranges from 0 for neutral grey to 10 for strong colours. It is the temperature (K) of a black body which emits radiation nearest in chromaticity to the light source being considered. BLACK BODY A “Perfect” emitter and absorber of radiation.g.Definitions
ADAPTATION The process of the eye adapting to brightness or colour. CHROMA An index of colour saturation. reflected light). CORRELATED COLOUR TEMPERATURE (CCT)(of a light source) This is used to define the colour appearance of a light source. APOSTILB (asb) A unit of measurement of the amount of light leaving a surface (i. COLOUR RENDERING INDEX (CRI) (of a lamp) Is a measure of a lamp's colour rendering ability. e.e. COLOUR TEMPERATURE (of a light source) The temperature of a black body which emits radiation of the same chromaticity as the light source being considered. BRIGHTNESS The subjective measurement of luminance. CANDELA (cd) Unit of luminous intensity approximately equal to one candle power.A Student's Guide
due to daylight. The axis is taken to be vertical unless stated otherwise. DISCOMFORT GLARE Glare which causes discomfort. DIFFUSE REFLECTION Reflected light from a matt surface.A Student's Guide
.Definitions CYLINDRICAL ILLUMINANCE The mean illuminance on the surface of a small cylinder located at a specific point in a room.
Interior Lighting Design . DISABILITY GLARE Glare which impairs vision. DIRECT LIGHTING Lighting in which most of the luminous flux reaches the working plane directly without reflection from other surfaces. (See also uniformity)
DOWNLIGHTER Direct lighting luminaire which emits light only within a relatively small angle to the downward vertical. DIRECTIONAL LIGHTING Lighting on a task predominantly from one direction. as a % of the horizontal illuminance outdoors. The unit used is lumens per watt (lm/W). EFFICACY The ratio of lamp luminous flux divided by the power consumed by the lamp. none of which predominates. (Unit Lux) DAYLIGHT FACTOR The illuminance at a point indoors. DIFFUSE LIGHTING ”Soft” lighting in which the luminous flux comes from many directions. (direct sunlight is excluded from both values). DOWNWARD LIGHT OUTPUT RATIO (DLOR) The ratio of downward light of a luminaire to its total light output. Where control gear is taken into account the unit becomes lumens per circuit watt. DIVERSITY The ratio of minimum to maximum illuminance (or luminance) over a specified area.
HUE The attribute of colour that enables an observer to classify it as red. and excludes white.normally taken on the working plane.
Interior Lighting Design . GLARE Discomfort or disability glare occurring when parts of the visual field are excessively bright. ILLUMINATION The process of lighting. GLARE INDEX A quantification of discomfort glare in an installation. INDIRECT LIGHTING Lighting in which most of the luminous flux reaches the working plane after reflection from room surfaces. INCANDESCENT LAMP A lamp which produces light due to its filament being heated to incandescence by current flowing through it. Unit: Lux ILLUMINANCE VECTOR This is a vector representing the directional flow of light. GROUP LAMP REPLACEMENT The replacement of all lamps usually after a specified period (usually 2 years) in an installation. GENERAL LIGHTING Lighting illuminating a whole area. FLICKER The visible modulation in light output due to the cyclic variation of a. etc.A Student's Guide
. It has both magnitude and direction.c. black and grey. (the shade of a colour). ILLUMINANCE (E) The level of illumination . FLUX FRACTION RATIO (FFR) The ratio of upward luminous flux to downward luminous flux.Definitions ENERGY MANAGEMENT SYSTEM (EMS) A computerised system for controlling energy use. blue..
. ISOLUX DIAGRAM A diagram which shows equal illuminance contours in an installation. (See maintenance factor) LIGHT LOSS FACTOR (LLF) This term has been replaced by maintenance factor in the 1994 CIBSE Guide. per square metre of floor area. INSTALLED POWER DENSITY The power needed. LAMP LUMEN MAINTENANCE FACTOR (LLMF) The proportion of light output of a lamp. after a specified number of hours operation. over a period of time. With discharge lamps this is usually taken after 100 hours of operation.Definitions INITIAL ILLUMINANCE Average illuminance in a brand new installation Em (Maintained illuminance) Eavi = ----------------------------------------MF (Maintenance factor) INITIAL LIGHT OUTPUT The luminous flux from a new lamp. Previously LLF and MF differed in that the latter took no account of the lamp lumen maintenance factor (LLMF). LIGHTING DESIGN LUMENS This term is now obsolete. to achieve 100 lux on a horizontal plane with general lighting. maintenance factor takes LLMF into account. LIGHT OUTPUT RATIO (LOR) The ratio of the light output of a luminaire to the light output of the lamps without a luminaire. In the 1994 Guide. (See maintenance factor) LAMP SURVIVAL FACTOR (LSF) The % of lamps still operating in an installation after a specified number of hours operation. It was given as the lumen output of a lamp after 2000 hours use. It was used to represent the average light output of a lamp throughout its life.
LOAD FACTOR The ratio of energy consumed by a controlled lighting installation to the energy which would have been consumed without controls.
Interior Lighting Design . to the initial light output of the lamp.
Definitions LOCAL LIGHTING . emits 4π lumens) LUMINAIRE This term supersedes the term light fitting. MAINTAINED ILLUMINANCE (Em) The average illuminance on the working plane at the end of the maintenance period. (A source of 1 candela. Brightness is a subjective term dependent on the person as well as other factors.Lighting illuminating a small area.
Interior Lighting Design . MF = LSF x LLMF x LMF x RSMF MAXIMUM ILLUMINANCE (E Max) The highest illuminance at any point of the working plane. uniform intensity. (UNIT: cd/m2) LUMINOUS FLUX (Ø) The light emitted by a source or received by a surface (Unit: Lumen) LUMINOUS INTENSITY (I) Describes the light output of a source in a given direction. LUMINAIRE MAINTENANCE FACTOR (LMF) The ratio of light output after a specified period of time to initial light output of the luminaire. It is the whole unit enclosing lamps.
LUMEN An SI unit of luminous flux. This takes account of dirt and dust reducing the light output of the luminaire. control gear.The SI unit of illuminance. (See maintenance factor) LUMINANCE (L) This is a measure of the objective brightness of a surface or a light source.A Student's Guide
. LOCALISED LIGHTING Lighting providing a higher illuminance over a particular area of an interior. MAINTENANCE FACTOR (MF) The ratio of illuminance at the end of the maintenance period to the initial illuminance. (Unit: Candela) LUX . 1 Lux = 1 lumen per square metre. Luminance is an objective measurement performed photometrically. diffusers etc. reflectors.
Definitions METAMERISM The phenomenon where coloured objects match under one light source but do not match under another. It is used to determine the Utilisation factor. where
L = Length W = Width Hm = Height of luminaire above working plane. This is an important factor when designing indirect lighting installations. REFLECTANCE Ratio of light reflected from a surface to the light received on it. MINIMUM ILLUMINANCE (E Min) The lowest illuminance on the working plane.
Interior Lighting Design . ROOM SURFACE MAINTENANCE FACTOR (RSMF) The proportion of illuminance at the end of the maintenance period to the initial illuminance taking account of the reduction in room reflectances because of dirt and dust.I. SCALLOPING A regular pattern of light and shade on walls. Operating efficacy = installed efficacy x load factor. This also refers to sources having the same apparent colour but do not have the same colour rendering properties.A Student's Guide
. MUNSELL SYSTEM Colour classification of room surfaces taking account of hue. L x W ---------------(L + W) Hm
R. OPERATING EFFICACY The efficacy of a lighting installation in use taking account of energy saving techniques. ROOM INDEX This takes account of room proportions and height of the luminaire above the working plane. (See maintenance factor) SCALAR (SPHERICAL) ILLUMINANCE (Es) The average illuminance on a very small sphere at a particular point in a room. value and chroma. It is separate to LMF and LLMF.
UNIFIED GLARE RATING (UGR) SYSTEM An internationally agreed numerical rating for discomfort glare proposed by Commission Internationale de l'Eclairage (CIE ) but not yet finalised.The area where an activity takes place requiring illumination. SPECULAR REFLECTION Reflection from a mirror or similar surface with no diffuse reflection. SPACE TO HEIGHT RATIO (SHR) The ratio of: Distance between luminaire centres. divided by their height above the working plane.
STROBOSCOPIC EFFECT An optical illusion where moving machinery may look stationary. or operating at a different speed to which it actually is. Direct sunlight is excluded from both values of illuminance. it is expressed as a % of the horizontal outdoor illuminance. This is caused by the flicker (modulation of light flux) of discharge lamps operating on a 50 Hz ac cycle.The ratio of light transmitted through a substance to the incident light.
Interior Lighting Design .Definitions SKY COMPONENT DAYLIGHT FACTOR (Dc) The illuminance directly received indoors at a specified point from a sky of assumed luminance. (See also diversity) UPLIGHTER A luminaire used for indirect lighting which directs its light onto the ceiling or upper walls. in a regular square array of luminaires. SPOT LAMP REPLACEMENT The replacement of lamps as they fail rather than group lamp replacement after a specified period. UPWARD LIGHT OUTPUT RATIO (ULOR) Ratio of upward (above horizontal) light output to the total light output of lamps. UNIFORMITY Ratio of minimum to average illuminance. TRANSMITTANCE .A Student's Guide
. normally taken on the working plane. UTILANCE (U) Ratio of light reaching working plane to light output of luminaires. TASK AREA .
VECTOR/SCALAR RATIO The ratio of illuminance vector magnitude divided by scalar illuminance. It depends on room index. room reflectances and type of luminaire used.g.Definitions UTILISATION FACTOR (UF) Proportion of light reaching working plane to light output of lamps. 6/12 means the person can read at 6m what the normal sighted person can read from 12 m) VISUAL FIELD The extent of what can be seen when looking in a certain direction. WORKING PLANE The plane in which the visual task lies.A Student's Guide
.8m above floor level. VISUAL TASK The visual work being performed. VISUAL ACUITY The ability to discriminate between objects placed very closely together. An optician measures acuity as the ratio of the distance a person can read a line on a chart to the standard distance which a person of normal sight can read the line.
Interior Lighting Design . (e. It is normally taken as 0.
Glass prism White light Source red orange yellow green blue indigo violet Fig.4.3).1. 1.up to 180 lumens per watt because its output is concentrated at the 380nm 720nm centre of the spectrum..Lighting Science. (See Fig. The constituent colours in a beam of light can be seen by passing the light through a glass prism (Fig.5)
380nm Fig. Fig. The human eye has evolved over millennia under the influence of natural light. Figure 1. etc. 1. 1.5 however. The eye therefore. It is not. has a very high efficacy . has a different mix of frequency components which produce a different colour light This is also true for indirect natural light which has been reflected or refracted and where some of the colour components have been absorbed in the process. This can be seen to follow closely the wave energy profile shown in Fig.4
A low pressure sodium vapour (SOX) lamp for example. or to use a more exact lighting term. is most sensitive to colours at the centre of the visible spectrum. The colour red for example will look brown under this lamp because there is no red in its light output. 1. 1. shows the sensitivity of the eye to different frequencies. their efficacy.1b.3 LIGHT SOURCES Light from natural sources such as the sun is known as white light and is made up from the different frequency components of the visible spectrum. Discharge lamps have concentrated outputs at or near the centre of the visible spectrum to improve their efficiency. capable of rendering colours at the periphery of the visible spectrum.A Student's Guide
1. tungsten filaments and gas discharge lamps.3
Artificial light from sources such as candles.
Lighting Science.6 shows the output of an incandescent lamp. When people view objects and room interiors under these lamps they experience slightly exaggerated colours which may in fact be desirable. 1. Note that most of its output is outside the visible spectrum and because of this it is a very inefficient lamp with a typical efficacy of 12 lumens per watt. The output of an incandescent lamp is higher at the red end of the spectrum giving it a characteristically warm output. Fig. Heat output is of course high because of the high infra red output. 1.A Student's Guide
. The output of a tri-phosphor fluorescent lamp is concentrated at the three primary colours of the spectrum (See Fig. Theory and Calculations
380nm Fig. Exact colour rendering is not provided by these lamps.8). 1.6 red 720nm
Fig.7). This provides an efficient lamp (up to 90 lumens per watt) with good colour properties. (See Fig.
Interior Lighting Design . It will have excellent colour rendering characteristics because all of the colours of the spectrum are contained in its output. 1.
infra red region blue 380nm Fig. (2800 K approx. 1. These lamps have much lower efficacies and provide a characteristically cool colour similar to the natural light of an overcast day in the northern hemisphere.8
If exact colour tasks are to be performed then colour matching lamps are necessary.). The northern sky is best because there is less variation of colour and no direct sunlight. 1.
2. the level of illumination on that surface is referred to as illuminance. unit.m. (not to be confused with Illuminance which is lumens received per sq.the flow of light. Colour rendering is also related to the illuminance on the task. 1. m.
Interior Lighting Design . season and weather conditions.4 LIGHTING THEORY Lighting can be considered in 4 stages. SOURCE . whereas luminance is objective.) and the unit used is “APOSTILB” which is not a S. the illuminated surface being considered a secondary light source. 1. Luminance is usually be measured in candela per square metre. source. flow.The fourth stage of this process is the light leaving the surface which has been illuminated by the source. FLOW .A Student's Guide
. 1. LUMINANCE (symbol L) .the light source has a luminous intensity (symbol I) and is measured in candela. illuminance and luminance.
Consider a situation where the same amount of light strikes both a “dark” surface and a ”bright” surface.I. Its luminance will therefore be much greater than that of the dark surface. The term brightness is a subjective term however.
3. or light flux (symbol φ) which is measured in lumens. A high illuminance (1000 Lux +) is recommended where exact colour rendering is necessary. ILLUMINANCE (symbol E) when light falls on a surface. The unit of measurement is lux. The illuminance is the same in each case but due to the greater reflectance of the “bright” surface it now becomes a secondary source of light. Luminance is measured in lumens emitted per sq.9
4. The luminance may be thought of as the brightness of the surface. Theory and Calculations
illuminance E Fig.Lighting Science.
The reflectance is 50%.10
.Lighting Science.1 The illuminance (E) on the working plane in Fig. Example 1.14 lm/m2
The luminance of a surface depends upon the amount of light arriving multiplied by the per unit reflectance R (p. 1. 1. L = E x R(p.u.10 is 500 lux. Theory and Calculations Note: 1cd/m2 = 3. 250 lumens/m2 are reflected by the surface.5 = 250 / 3.).14 Apostilb = 3. working plane Fig.) = 500 x . calculate the luminance of the working plane.14
Lightmeter A (500 lux) If the reflectance of the workin plane is 50%.u.
5 LAWS OF LIGHT 1.5 lux d2 42 I 1000 E = -.2 Inverse Square Law In Fig.= ----= 250 lux 2 2 d 2 I 1000 E = -.
Fig.5.11 the area illuminated by the point light source increases in proportion to the square of the distance.5. Theory and Calculations
1.= -----= 62.2 A point light source has an intensity of 1.
Example 1.000 candela and the light falls perpendicularly on a surface.000 km/S and requires no illuminated medium for propagation. I 1000 d E = -. This means that light travels in straight lines. (ii) four metres and (iii) six metres. I E = ---d2 where d = the distance between the source and the object.
In the example shown the illuminance reduces to a quarter of its original value when the distance is doubled.12 2 2 d 6
Interior Lighting Design .1 Rectilinear Propagation of light. 1.11
1.8 lux Fig.Lighting Science. It follows that the average illuminance would decrease by the same ratio. area It travels at 300.A Student's Guide
. 1. I Calculate the illuminance on the surface if its distance from the surface is: (i) two metres.= -----= 27. 1. Similarly the illuminance reduces to one ninth of its original value when the distance away is tripled.
1. The rays of incident light may be taken as parallel.
2000 -----.14a
Interior Lighting Design .Lighting Science.5.A Student's Guide
.= Cos θ BC where θ = The angle between the incident light and the normal to the surface BC.8 -----------52
Fig.= d2
2000 x 0. Fig.= 125 lux 42
I Cos θ Eb = --------.
d2 Example 1. the area illuminated increases reducing the average illuminance by the same ratio. Calculate the illuminance on the surface directly underneath (Ea) and at a distance of 3 metres to the side (Eb).3 Cosine Law
When light does not fall normally on a surface.000 candela in all directions and is mounted 4 metres above a surface. 1.3 A point light source has an intensity of 2. 1.13 θ
AB ---.13 shows light from a distant source striking surfaces AB and BC.
The total illuminance at: (i) the base of each lamp post.= --------x2 x2 Ea Cos3θ
Ea Fig. Calculate the illuminance contributed by each lamp: (a) (i) (ii) (iii) (iv) directly underneath.= ------y2 y2
multiply above and below by x2 /y2 I (x/y)3 I Cos3θ --------.
(c) Sketch an illuminance profile on a straight line joining the base of each lamp post. 8 metres from the base. Theory and Calculations
Note: Ea = I -x2 I Cos θ I . 16 metres from the base.4 A walkway is illuminated by Son 250W lamps each having a luminous intensity of 4750 candela in all directions below the horizontal.14b
i.Lighting Science. (ii) midway between the base of each lamp post.Eb =
. 32 metres from the base.e.
Interior Lighting Design . Each lamp is installed at a height of 6m and the distance between them is 16 metres. x/y -------.
(a) I Ea = --.= d2 θb = 4750 ------62 tan-1 (8/6) = 132 Lux 53.15b 59 lux
. etc.38 o = 5.71 lux 0.83 lux
Ec 145 lux Fig 1. B. Eb.44 o = 132 Cos3 79.13 o 132 Cos3 53.13 o = 28. C and D be Ea. respectively.15a Eb Ec Ed
Let the illuminance at A.Lighting Science. Theory and Calculations
6m Ea 8m 16m 32m Fig 1..51 lux 132 Cos3 69.
Fig 1.Lighting Science. (taking A as centre and adding the contributions from two lamps either side)
(b) The total illuminance at: (ii) midway between the base of each lamp post. = = = 2Eb + 2 Ed (approx.) 57.15c
(b) The total illuminance at: (i) the base of each lamp post.A Student's Guide
.66 = 145.66 58.42 + 1.68 lux.08 lux.
= Ea + 2Ec + 2 Ed = 132 + 11.02 + 1.
= 796.16
There are 2π radians in a circle and 4π steradians in a sphere. In 1948 an international standard was adopted for light intensity. cd 4π 4π
Interior Lighting Design . φ = 500 x 20 = 10000 lumens φ 10000 I = ---.5. The Steradian. Example 1. It is defined as the luminous intensity of a point source at the centre of a sphere of 1m radius which produces an illuminance of 1 lux on the inner surface of the sphere. the surface area of the sphere = 4πr2 Therefore the surface area of a 1 metre radius sphere = 4 π m2 I E = -.5 A 500 watt Tungsten Halogen lamp has an efficacy of 20 lumens per watt.A Student's Guide
. Consider a sphere of radius one metre.4
The Candela. 1.
Fig. This is like a three dimensional radian.= -----. Calculate its mean spherical intensity. sometimes called the unit solid angle. CONCLUSION: A lamp with an intensity of 1 candela produces 4π lumens of light flux. The steradian is the solid angle subtended at the centre of a sphere by surface areas equal to r2.Lighting Science. with a symmetrical point light source of 1 candela intensity at its centre. The candela (pronounced “candeela”) is approximately equal to one candle power. Theory and Calculations
1.= 1 lux = 1 lm/m2 d2 If there are 4π m2 then the source must produce 4π lumens in order to produce an average illuminance of 1 lumen/m2 on the surface of the sphere.
4. Theory and Calculations
Interior Lighting Design . the light intensity in a given direction is found from polar diagrams supplied by manufacturers. is negligible. Polar curve data is also supplied by lighting manufacturers in software packages to allow accurate calculation of illuminance in schemes with zero reflectance. (see Example 1. We have already seen that the light output in a given direction is called the luminous intensity. A more realistic output for a bare lamp would be as shown in the same diagram by curve B.
Fig. It may also be suitable for indoor schemes where the light reflected onto the working plane from walls.18 by curve A. the output would be concentrated even more as shown by curve C.6 POINT SOURCE CALCULATIONS This method of calculation is particularly suitable for outdoor schemes. If reflectors were used. ceilings etc. then 80 cd/1000 lm would be its intensity in all directions as shown in Fig. If the light source was symmetrical in output as in example 1.4) with a small number of light sources and when it is necessary to calculate the illuminance at a small number of points. 1.Lighting Science. They are also used to provide the designer with information on light intensity in a given direction when using the point to point method of calculation. Computer programmes have allowed this method to be extended to schemes with a large number of sources and where the illuminance must be calculated at a large number of points.18
Polar diagrams allow the lighting designer to select suitable luminaires and spacing distances based on an acceptable illuminance variation along the working plane.1 POLAR DIAGRAMS Light sources are seldom symmetrical in output. 1.1. The point to point method uses the inverse square law and cosine law.A Student's Guide
= 35.18 calculate the illuminance on a horizontal surface which is 2 metres beneath the source: (i) (ii) directly beneath. 1. the incident angle is 45 o. 2 metres to one side. the intensity at a 45 o angle = 200 x 2 = 400 cd. 1.707 -----------. I 400 x Cos 45o ∴ E = ---.18 must be multiplied by 2 because the output of the luminaire is 2000 lumens and the values are quoted per 1000 lumens.35 lux 8
Interior Lighting Design .Cos θ = --------------.= ------.Lighting Science. the intensity directly under the lamp = 250 x 2 = 500 cd.18).= d2 22
(ii) From Fig 1. I 500 ∴ E = ---. From the polar curve (Fig.18. 1.= d2 2.18a
All values in Fig.822
400 x 0. 1.A Student's Guide
. 1. (i) From Fig. Theory and Calculations
Example 1.18a.6 A point light source has an output of 2000 lumens and intensity as shown by curve C in Fig.
2m Fig.
Calculate: (i) (ii) The illuminance on the working plane directly under the lamp The illuminance on the working plane 2 metres to one side.19a
Fig.19.828 m I Cos θ -------d2 675 x 0.707 ------------(2.7 A point source luminaire has an output as shown by the polar curve in Fig.A Student's Guide
.828)2 = 60 lux
45 deg 2.19
1500 = 750 x -----------.828m
45 deg 2m Fig. It is mounted 2 metres above the working plane and is fitted with an 18 Watt compact fluorescent lamp whose output is 1500 lumens.= 1125 cd. 1.25 lux
from Fig.828 =
0.1. 1. d = 2. 1. 1000
281. Theory and Calculations
Example 1.Lighting Science.707
Interior Lighting Design .19a.
1. Light is transmitted through it. Heating engineers normally consider all of the lighting load as a heat gain in the room on the basis that all of the light is eventually absorbed as heat in the totality of room surfaces.Lighting Science. 1. 2. It therefore follows that: Reflected Light Reflectance = -----------------Incident Light 1.4 Indirect Lighting Schemes Indirect lighting schemes rely on reflected light from room surfaces to illuminate the working plane. This can be achieved by using low chroma (pastel) colours on the room surfaces. 1.7. are referred to as translucent.
When light falls on a surface.7.2 Reflectance We have already seen that the luminance of a surface is the illuminance on it multiplied by the surface reflectance. 1. one or more of the following may occur: 1. This is the reason light coloured high reflectance clothing is preferred in summer.7. High reflectance surfaces are necessary if the scheme is to be efficient. 3.3 Absorption The light which is not transmitted or reflected is absorbed as heat.
Interior Lighting Design . Light is absorbed as heat. colours of surfaces must be carefully selected so that the reflected light from these room surfaces is not colour distorted. In addition. Light is reflected from it.1 Transmittance Most surfaces will not allow light pass through them but surfaces which do.7
TRANSMITTANCE.A Student's Guide
K. in 1973 for general office lighting. This recommended illuminance must be maintained throughout the life of the installation and must take account of the reduction of light reaching the working plane because of lamp ageing. 3.1 A Historical Perspective Research work on determining appropriate illuminance levels began in the 1930's. The importance of the visual task and the consequences of errors. It is therefore important to consider a lighting scheme not only in terms of quantity but quality as well. The subsequent oil crisis brought about a reduction of recommended levels in the U. at which point it levelled out. The onset of fatigue could be delayed by increasing the illuminance to levels above 400 lux. remained unchanged. Modern research has also shown that visual task performance is also related to the colour of the light and contrast.E. Visual performance was seen to improve as the illuminance was increased up to 400 lux. The CIBSE Code for Interior Lighting Design (1994) gives recommended maintained illuminances for a wide variety of installations.S.Lighting Science.8. This value was used in the U.) 1. The level of illuminance required depends on 4 factors: 1.S. Theory and Calculations
1. dust collection and deterioration of the decor. The eyesight of the user. however. etc. The difficulty of the visual task. were 1500 to 2000 lux.S. A link was established between the illuminance and the performance of visual tasks. The design illuminance (maintained illuminance) is taken as the illuminance at the end of the maintenance period (typically 2 years). (refer to vector/scalar values.K. A norm of 500 lux was recommended by the I. This is different to the method used in previous codes which used the lamp output at 2000 hours (LDL) to calculate the average illuminance over the life of the installation. 4.2 Current Practice.8 Illuminance ( E) and Visual Performance. In this regard vertical illuminance is also considered important.8. at the same time the recommended levels in the U. 1. modelling index. The duration for which the task is undertaken. but those in the U.
Interior Lighting Design . 2..A Student's Guide
. This reflected a difference in emphasis and a different regard for the consumption of energy.
In general. Fatigue can be offset by using high illuminance levels.8. For the average person. visual performance improves as illuminance increases. reading and writing is easiest when the illuminance is about 1000 lux. however.8. Theory and Calculations
1. 1. an illuminance of 500 lux is recommended for offices where the task is mostly desk based (300 lux if screen based).
Interior Lighting Design .8. 1.1 Importance of task Performing a heart operation may not prove any more difficult visually than assembling a piece of machinery.8. Notwithstanding the above.4 Eyesight of user. at very high illuminance levels glare becomes a problem and may even cause a reduction in performance. It is clear that performance improves significantly up to a certain illuminance after which there is no further significant improvement. 1.3 Duration of task The duration of the task is also important Higher task illuminances increase the optical depth of field thereby reducing the work required by the eye in adjusting focus.Lighting Science.2. The average 70 year old requires up to 3 times the task illuminance of the average 20 year old.
illuminance Fig. 1. This seems a reasonable compromise between performance and energy conservation.2 Difficulty of task. in current European practice. Human eyesight deteriorates with age and so older people require a higher illuminance for a given task than younger people.2.A Student's Guide
.2.2. It is clear that the importance of the task is a major consideration.20 shows the relationship between visual performance and task illuminance. Nonetheless if one were on the operating table one would hope there would be sufficient light to allow the surgeon perform the operation with maximum efficiency and without error. It is also clear that a higher illuminance is required as the task gets more demanding.
. The lumen method. (φ . The following formula is used: N (n . For external applications or where the reflectance of the surfaces is unknown or may not be relied upon (emergency lighting schemes). φ) .9
This method is most suitable for interior lighting design . UF -------------------A
or N = ExA ----------------Mf . a utilisation factor for zero reflectance may be used. Theory and Calculations
1. is normally used to calculate the average illuminance on working planes. UF . where a high proportion of light on the working plane is reflected by internal surfaces.Lighting Science. n)
Interior Lighting Design . MF . or to calculate the number of luminaires required to provide a specified average illuminance in rooms. sometimes called the luminous flux method of calculation.
Table 1. Consider an installation where lamps are to be replaced after 6000 hours use. This figure is now divided by the initial lamp lumens to get the LLMF.1 Number of Lamps / Luminaires. N is used to represent the number of luminaires and n is used to represent the number of lamps in each luminaire.9. Calculation of the maintenance factor is detailed on the following pages.200 500 750 1000 750 500 300 750
Interior Lighting Design .2 Lamp Flux (φ lumens) The initial light output (100h) is now used for calculations.9. A factor called the lamp lumen maintenance factor (LLMF) is then applied to allow for the reduction in light output from the lamp during the maintenance period.21 6000
Note: This is a change from the 1985 code which used the output at 2000h called the lighting design lumens (LDL). 1. The lamp manufacturer's data is checked to see the lamp output after 6000 hours use (as shown in Fig 1. Theory and Calculations
1.1 Typical recommended maintained illuminances Corridors and stairs Warehouses Medium bench and machine work Fine painting spraying and finishing Printing inspection Proof reading / drawing offices General offices (desk based) General offices (screen based) Supermarkets Lux Limiting glare index
initial lamp lumens (100 hrs) lumen output old LDL at 6000 hrs lumen output 100 2000 hours Fig.A Student's Guide
. 1.Lighting Science.21).
1.Lighting Science. The Lamp Survival Factor (LSF) will be 1 if spot lamp replacement is carried out.
hours Fig. 1. 1. Theory and Calculations
luminaires cleaned after 3000 hrs 3000 hrs hours Fig.
Reduced reflectances due to the accumulation of dirt and dust on room surfaces.22b 6000
4.(LLMF Fig.22c
Reduced light output due to the Lamp Lumen Maintenance Factor. 1. 1. Room Surface Maintenance Factor. Maintenance Factor (MF) is the term used to take account of the reduction in illuminance over the maintenance period due to: 1. Reduced light output from the luminaire due to the accumulation of dirt and dust on the luminaire.22c) Reduced light output due to lamps failing. deterioration of room surfaces as well as the
hours Fig.21 and 1. which took account of the reduction in light output due to the accumulation of dirt and dust on luminaires.
100 80 (LLMF) light loss due to % (E) lamp ageing.22a
MF = RSMF x LMF x LLMF x LSF Note: The CIBSE Code for Interior Lighting 1985 used the term Light Loss Factor (now obsolete).22b). (RSMF Fig. 1.9. Luminaire Maintenance Factor.22a). Manufacturer data will give the percentage lamp failures for a specific number of hours operation.(LMF Fig.3 Maintenance Factor (MF) In the 1994 guide.A Student's Guide
Lighting Science.6 reproduced the Code for Interior Lighting by kind permission of the Chartered Institute of Building Services Engineers.
Table 4. Theory and Calculations reduction in light output due to lamp depreciation.4
Interior Lighting Design .3 Table 4.2 to 1.A Student's Guide
Table 4.Lighting Science.5 Table 4.
. Theory and Calculations Table 4.7
1. The room reflectances are Ceiling 0. Theory and Calculations
Example 1.558 (say 1.9.5 x 5.
1. 1.5)
From Table 1. Calculate the minimum number of luminaires which must be installed to conform with a recommended SHR of 1. This is expressed in terms of the Uniformity Ratio (see definitions).P. Point source luminaires are suspended 1.(1.5 metres below ceiling level. 10 A factory area is 40m long. Height 3m.5 + 1) = 5.9 Calculate the Utilisation Factor for a room with the following dimensions: Length 8m.5m
8 .A Student's Guide
. Ensuring that luminaires are spaced within the recommended value will mean an acceptable variation in illuminance across the working plane.24
Manufacturers will specify a recommended SHR for each of their luminaires.5 = 8. 1.
Example 1.5 SPACE: HEIGHT RATIO (SHR) This is the ratio of space between luminaires (S) to their height above the working plane (Hm). Width 6m.5m
8m W.= (L + W) Hm 8x6 -----------(8 + 6)2.I.5 : 1
1.3 and Floor 0.5 : 1.25m
Interior Lighting Design .8 the Utilisation factor can be read as 0.8m.2
1. Walls 0.2.0m
therefore S = 1. LxW R.5. 20m wide and is 8m high. Fig. = -----------. The working plane is 1 metre high.25
SHR = 1. height of working plane 0.Lighting Science.
a spacing of 0.0 4. Theory and Calculations
W 20 Min.33 8.25 L 40 Min.67m.e.0 4.0 8. the actual spacing is determined as follows: W 20 Spacing between rows (S) = ----------. No of rows 3 Note: The spacing between the last row and the wall should < 0.= 6.85 (5 luminaires)
This means that the minimum number to conform with SHR.67 3.Lighting Science.= 2. of rows = --.33 S to the wall may be used. i.
Interior Lighting Design .= ---. no.= ---S 8. More than this number can be used if desired for reasons such as balance.A Student's Guide
. Assuming that three rows of five luminaires is suitable.4 (3 rows) S 8.33m L -----------= No per row 40 -----.= ---.25
= 4. requirement is 3 rows with 5 luminaires per row.0 6. control or ease of installation.0
Note: If work is to be carried out at the perimeter of the room.0 8.< 3.26 8.= 8m 5
Layout diagram 40m 3. no. effect.67 20m 6.33 Fig. of luminaires per row = --. 1.5 S.
10 is to be illuminated using continuous rows of twin 1500mm fluorescents. it is common practice to use continuous rows of luminaires with the transverse spacing at the maximum permissible. 36 x 1.5m and the following SHR's apply.11 The factory in example 1.6m approximately. Design a suitable layout given a mounting height above the working plane of 5. i. particularly where luminaires are suspended below the ceiling.00 : 1 (spacing between rows) Axial 1.e. which is longer than the building. this would mean using 36 luminaires per row and these would not fit in the 40m available.
Fig.75 : 1 (spacing in rows) (i) Spacing between rows: Hm = 5.5 x 2 = 11m
Two continuous rows of fluorescents 10 metres apart and 5 metres from each side wall would conform with the SHR requirement.5m.5m tubes is 1. Theory and Calculations
Linear Luminaires The relevant spacing maximum transverse and axial spacing data will be supplied by the manufacturer. therefore S = 5. installation costs will be kept to a minimum. The lighting installation must however be co-ordinated with other services and compromise with air conditioning outlets and other ceiling mounted equipment is often necessary in practice. In this way. Transverse 2.27
Example 1.Lighting Science. Calculations indicate that 72 luminaires are required. (Note: the maximum recommended transverse SHR is usually different from the axial SHR where linear luminaires are used).A Student's Guide
. Where high levels of illuminance are required. 1.
Interior Lighting Design .5 = 54m. The spacing is usually taken between centres. Note the actual physical dimensions of luminaires with 1.
83 3.K. Since this is less than the maximum spacing.29
Interior Lighting Design . 1. (ii) Sketch a layout of the scheme indicating the spacing between luminaires.0m 2.07 6.5 n = 4 lamps φ = 1400 lumens 500 x 128 N = ---------------------. Theory and Calculations
40 Try 3 rows of luminaires with 24 luminaires per row.= 30. the luminaires will be spaced 1. (--.12 An office area measures 16m x 8m and is 2.75 x 0.7 metres high.5 and maintenance factor is 0.e.7m
Fig. 1.= 0.83 m from end walls 2 The transverse spacing is now 20m divided by 3. E x A = -------------------MF x UF x (n x φ) E = 500 lux A = 16 x 8 = 128m2 MF = 0. It is to be illuminated to an average value of 500 lux. Utilisation factor is 0. the effect will give a more uniform distribution of light.75. 0.33 6.Lighting Science.A Student's Guide
Fig. each containing 4 lamps are used.) seems O. (i) Calculate the number of luminaires required. 600mm x 600mm recessed luminaires.67m.67 1. 24
0. Each lamp has an output of 1400 lumens.67 gap 0.75 UF = 0.5 luminaires.7m 0.67 ---.28
Example 1.67m apart (centre to centre) and 1. which is 6.67
i.5 x (4 x 1400) N
2.67m.= 1.
(in practice tiles will normally restrict spacing to multiples of 0. An alternative layout would be 4 rows of 8 luminaires. In practice it is likely that ceiling tiles would restrict spacings to multiples of 0.A Student's Guide
16. There are no restrictions with regard to ceiling tile positions.e.7 (i. Desk height 0.6m between centres.5 : 1.6m. 8 Min. no of rows = ---3
3 rows of 10 would give a spacing of 1.0m 2.Lighting Science. Therefore max spacing = 3 metres 3.6m (the size of the ceiling tiles)
Interior Lighting Design .0m
Fig.0m
2.7m therefore Hm = 2 m 2. SH ratio = 1. Theory and Calculations
Assumptions: 1. 1.
0.64 0.Lighting Science.59 0. The ceiling to desk height is 2 metres.54 0.57 0.A Student's Guide
.3 lamp survival factor)
Maintenance Factor (M.64 4.53 0. Utilisation Factors Room index
0.50 0.9.9.52 1. find the utilisation factor. Using tables 1.50 0. L x W 30 x 15 Room index = --------------.95 x 0. (a) (b) (c) Using Table 1. Each lamp has an initial output of 85 lumens per watt.75 0.00 0. The top row of the table applies.68 0.67
Table 1.12 An office area measures 30m x 15m.3 0. The lamps are operated for 6000 hrs (2 years) before being replaced..48 1.64 0.7 0.66 0.65 0.00 0.69 0.636
Interior Lighting Design . The area is to be illuminated to a general level of 500 lux using twin lamp 32 watt VDT luminaires with a SHR of 1.3 lamp lumen maintenance factor) 0. U F = 0.6 room surface maintenance factor) 0.= -----------.) = LLMF x LMF x RSMF x LSF = 0.95 = 0. Calculate the number of luminaires required and design a suitable lighting scheme.00 0.87 (Table 1.9
SHR (nom) 1..5 0.62 0.1 Solution:
(a) assume a bright interior with room reflectances 70% ceiling.66 5.2 0.. Theory and Calculations
Example 1..67 0.57 0.57 2.= 5 (L + W) H m (30 + 15)2 from the table 1.5
Room reflectances C W F 0.69 0.63 3.F.55 1.95 (Table 1.2 to 1.25 0.61 2. Lamps and luminaires are cleaned annually and the room is cleaned every 3 years.87 x 0..5 luminaire maintenance factor) 0.67 0.00 0.81 x 0.00 0.25.60 0.81 (Table 1. 50% walls and 20% floor..6 find the maintenance factor.95 (Table 1.62 0.50 0.
SHR = 1.= 1.875m.25m 30m Fig 1.= 2. allowing 16 per row 30 15 Axial spacing ----.69 x 2720 x 2
Hm = 2m.Lighting Science.636 x 0.50m
1.5m 15 Number of rows required = -------2.5 = 6
Round off number of luminaires to 96.5m 16 6
1.875m 0. Transverse spacing = ---.25 ∴ max spacing = 2.A Student's Guide
φ = 85 x 32 = 2720 lumens per lamp 500 x 30 x 15 N = ---------------------------0.94m
. ExA 500 x 50 x30 -------------. A general lighting scheme is to illuminate the whole area to 500 lux maintained illuminance using 1000 watt metal halide lamps with an initial efficacy of 90 lumens per watt.5 : 1 is recommended for the luminaire chosen and a mounting height of 5m over working plane is assumed.= 27. 4 rows of 7 spaced as shown is an acceptable design.7 MF x UF x φ 0. 1.000
therefore 28 lamps are required. Maintenance factor is 0. Theory and Calculations
Example 1. Check space height ratios for length and width.32
Interior Lighting Design .Lighting Science. A space height ration of 1. φ = 1000 x 90 = 90. There will be a reduction in lamp output over time but this is taken account of in the maintenance factor.6 and utilisation factor is 0.= ----------------------.000 lumens per lamp initially.5.13 A factory measures 50m x 30m x 6m high.75m 7.5m
Fig.5 x 90.6 x 0.
50m 3. Design a suitable lighting scheme.
Lighting Science.A Student's Guide
. Giving reasons for your choice.
Solution 1: i Lamps .
2 Determine the utilisation factor for the factory described in question 1 using table Q2 and assuming that the surface reflectances are: Ceiling 50%.HPMV (MBI) . Walls 50% and Floor 20%.
Interior Lighting Design . 3 Using the CIBSE code for interior lighting determine the most suitable maintenance period / Maintenance Factor for the factory described in question 1 Assume that the following applies: i tri-phosphor lamps are used ii The factory works a double shift six day week iii The luminaires are maintenance category C iv The environment is described as normal v The luminaire flux distribution is direct/indirect 4 Design a suitable general lighting scheme for the area described in question 1 and sketch a layout of the proposal.Metal Halide Both lamps have high efficacy and good colour rendering ii Luminaires
Reflectors ensuring a high Downward Light Output Ratio (DLOR) are recommended as these luminaires are normally suspended and/or ceiling voids often have low reflectances in factories.LPMV . The factory is to be provided with general lighting to a level of 300 lux.tubular fluorescent . Theory and Calculations Sample questions
1 A Factory area measures 30m x 15m and is 5m high. specify for the above installation: i ii two suitable lamp types two suitable luminaire types.
Interior Lighting Design .5) RSMF 1 yr.71 0. C = 0.85 x 1.73 0. (medium/large) (direct/indirect) = 0.00 0.0 x 0.= (30 + 15) x 4
2.58 0.85 (table 1.A Student's Guide
.3 0.e.63 0.72 0.00 0.75 NA NA NA 1.25 0.89 2yr.59 1.88 = 0.69 0.85 Recommended cleaning period is 1yr.88 = 0. The number of hours of usage per year = 5000 (table 1.81 x 0. + spot lamp replace + group lamp replace every 2 year (MF = 0.68 0.61 2.81 (table 1.4) LMF 1 yr. a 20% energy saving compared with option (i). (MF = 0.69 Solution 3 Determine the Maintenance period / Maintenance Factor
Using the data provided and tables 1.2 0.69 5.6) MF = LLMF x LSF x LMF x RSMF Alternative maintenance schedules: (i) (ii) (iii) Clean every year.85 x 0.85 x 0.00 0.63 0.61) Clean and group lamp replace every 1 year 3 months. (table 1.70 0.5
Table Q2 Room reflectances C W F 0.72 0.68 0. = 0.Lighting Science.56 1.64 2.68 4.00 0.63)
Select option (ii) and benefit from a maintenance factor of 0. cat.65 0.81 x 0.0 x 0.89 x 1.61 (i. = 1 2yr.88 (table 1.2) LLMF 1yr.50 0.81 x 0.69 0.71
Utilization factor = 0.6. (MF = 0.88 = 0.51) Clean every year. Theory and Calculations
Determine Utilisation factor.50 0.1
0. 30 x 15 --------------.60 0.4) LSF 1yr. = 0.5 0.61 0.66 3. = 0. + group lamp replace every 2 years.5 0.66 0.2 to 1.
Interior Lighting Design . ExA ----------------Mf .
Assume mounting height (Hm = 3.85m
30 luminaires provide an overall average maintained illuminance of 293 lux which is deemed acceptable.A Student's Guide
.69 (5220 x 2) = 5220 lumens
30.P.7 (say 31)
Three rows of 10 luminaires would be a possible solution.5m 5m 15m 3m 1.Lighting Science.0m 5m 3.0m 30m 2.
1.5m 1. UF . SHR of 1.5m) and a max. lamp φ = 58 x 90 assume twin tube luminaires.61 x 0. n) 300 x 30 x 15 -------------------------0.5 = 5.5 Maximum spacing = 3. Theory and Calculations
Solution 4. (φ . Using linear 58W 1500mm tri-phospor fluorescents.5m W.
Visual stimuli are important such as colours and textures. Conspicuous reflections such as scalloping must be avoided.A Student's Guide
.10.10. This does not however. however care is necessary to ensure that undesireable shadows are not cast. Nonetheless an uplighting scheme is less efficient than standard ceiling mounted scheme by about 10% to 20%.2.1 Introduction.2 CALCULATIONS 1. The following formulae apply: ExA N = ----------------φ x n x MF x UF UF Where: = ULOR x TFCF Utilisation factor for uplighters upward light output ratio of luminaire transfer factor (see table 5. These colours should not form part of the main reflecting surfaces.10 UPLIGHTING 1. Theory and Calculations
1. .10. 1. Maximum and average ceiling luminances must also be calculated to ensure a satisfactory result (see chapter 6)
Interior Lighting Design . ensure that the illuminance variation over the working plane is acceptable. A room illuminated by uplighting will appear bright and airy though perhaps a little boring. These surfaces act as secondary sources providing soft diffused lighting to the room. There will be no excessive glare from VDT screens irrespective of the viewers position provided there are no stark contrasts of room surface luminances. Uplighting may be used to enhance the architectural features of interiors.1 To Calculate number of luminaires required The lumen method of calculation may be used but there is a change to the use of UF. Ceilings and walls should be matt with high reflectance and white or pastel colours.Lighting Science. Uplighters illuminate the ceiling and upper walls.21 from CIBSE code for interior lighting) Number of luminaires Maintained average illuminance (lux) Area of room (m2) Initial bare lamp lumens (lm) Number of lamps per luminaire Maintenance factor Utilisation factor
The number of luminaires required can be calculated from this formula.
4 2.7 Lamp Data Luminaire Data Typical nameplate markings Safety Classes Fire protection Ingress protection Using data to design a lighting scheme
Interior Lighting Design .2 2.5 Lamp Terminology Lamp Types Environmental Effects of Light Sources New Lamp Developments Summary of Lamp Data
Section 2.1.1 2.1 2.3 2.3.A Student's Guide
.1.2 LUMINAIRES 2.1 LAMPS 2.3.4 2.3.1 2.3.2.2.6 2.3 2.1.4 2.1.3 2.5 2.Lamps and Luminaires 49 ________________________________________________________________________
Section 2.3.2.2 2.3.2.2.2 2.5 Luminaire Constructional Features Control of Light Output Glare Visual Display Terminals Luminaire Selection for Offices
Section 2.1.3.3 MANUFACTURERS' TECHNICAL DATA (for lamps and luminaires) 2.
lamps will normally be replaced in bulk (group lamp replacement) after a specified number of hours operating or after a certain percentage of lamp failures.1 LAMP TERMINOLOGY Before considering each lamp type individually and comparing characteristics it is important to become familiar with some lighting terms.Lamps and Luminaires 50 ________________________________________________________________________ 2. Luminous Efficacy (lumens per watt) This is the light output of the lamp in lumens divided by the power input to the lamp in watts. For this reason. Less likelihood of electrical damage to control gear because of a faulty lamp. 3. it should be noted that the light output of a lamp declines with age. will be higher.
4. Interior Lighting Design . The number of lamp failures may be used as a condition monitoring parameter to determine the replacement period. The advantages of group lamp replacement are: 1. The alternative is to use a calendar period as an estimate of lamp usage. The control gear power loss (10% for high frequency and 20% for low frequency lamps is not included in this calculation.F.
. The term Luminous Efficacy is now quoted for the initial lamp output (first 100 hrs). The maintenance period is often made to coincide with company holidays.A Student's Guide
2. Lamp Life Survival Factor (LSF) This relates to the percentage of functioning lamps in an installation after a certain period of use.the lower will be the energy usage resulting in lower energy costs and less environmental emissions. 5. Lamp disposal is more easily planned. Less lighting installed initially because the M. One planned maintenance operation resulting in less disturbance and lower maintenance cost. Lamp Replacement Many people relate lamp replacement to lamp failure. Efficacy is directly related to energy costs. Uniformity of lamp colour. Group Lamp Replacement (Planned Lighting Maintenance PLM) This normally takes place in an installation when approximately 10% of lamps have failed. The term efficiency is sometimes used but strictly speaking this is not correct because the output and input are measured in different units. The higher the efficacy .1.
Colour Rendering Index (Ra) Ra = 90 90 = Ra = 80 80 = Ra = 60 60 = Ra = 40 40 = Ra = 20
Lamps from group 1A have a colour rendering index greater than 90 and would be used where accurate colour rendering is required.I.E. (See Table 2. a red car driving along a motorway illuminated by low pressure sodium vapour lamps will appear brown or grey because there is no red in the output of a LPSV lamp . Paradoxically the lower the CCT.as illustrated in Fig. Lamps from group 1B are widely used for interiors where colour is important but not critical. The most widely adopted method of indicating colour rendering performance of lamps is the CIE colour rendering index (C. The colour appearances of a surface depends upon the spectral composition of the incident light.
. Lamps from group 4 are likely to produce a marked distortion of some colours.Lamps and Luminaires 51 ________________________________________________________________________ Correlated Colour Temperature (CCT) This relates to the colour of the light emitted.I. 2.R. If the light output of a lamp does not contain the colour red then surfaces which are red will become colour distorted when illuminated by this lamp.3. Table 2.1B Colour rendering group 1A 1B 2 3 4 C. Lamps from group 3 will not render colours accurately but on the other hand do not produce a marked distortion of colours either. Table 2.). Generally a warm appearance is desirable where illuminances are low .1).below 300 LUX. the warmer is the CCT class. For example.1A CCT Class Warm Intermediate Cool
Colour Rendering This refers to the ability of a light source to render colours accurately.
but as this is at such a high frequency (35 kHz).5
Low efficacy. providing good colour performance (CRI IB) and high efficacy . Exact colour rendering however. low colour renderin Fig. In recent years lamp manufacturers have developed lamps which are very efficient and have good colour performances.5). Colour preference is a term used to refer to human reaction when seeing objects illuminated by these lamps. Discharge lamps pass through a “Dark Period’ one hundred times a second at a frequency of 50 Hz. 2. is not provided. (See Fig.up to 85 lumens/watt. the poorer was its colour rendering performance. Whilst colour rendering with these lamps is not exact they perform well with regard to “colour preference”. it does not cause danger or discomfort. High frequency lamps also flicker. green and blue). 2.3
Tri-phosphor fluorescent lamps emit light output which is concentrated in the 3 primary colours of the spectrum ( red.
High efficacy. Stroboscopic Effect and Flicker Stroboscopic effect is the visual phenomenon whereby rotating machinery may appear to look stationary or rotating at a different speed or direction than it really is. good colour rendering Fig.A Student's Guide
High efficacy. Primary colours appear to have a stronger hue and this is acceptable and pleasing to the people using the interior.Lamps and Luminaires 52 ________________________________________________________________________ Efficacy Vs Colour Rendering There was a general rule at one time that the more efficient a lamp was. This flicker not only causes stroboscopic effect but also causes discomfort to people in the area and may contribute to sick building syndrome. good colour renderin Fig. 2. 2.
instant light.2. no control gear. normally argon.
Fig. The operating temperature is limited by the melting point of the filament. 2. (e. 2.g. 2.2 LAMP TYPES Incandescent Lamps and Discharge Lamps. Applications: Domestic and short duration use in commercial and industrial installation.hence its inefficiency. good colour rendering.5
Efficacy :10-20 Lumens/Watt (Typically 13 lm/W for a 100W GLS .1. cleaner’s store).A Student's Guide
. high heat output. good colour rendering Fig. (See Fig. (This increases dramatically on reduced voltage) Colour rendering: Excellent (1A) Colour Temperature: 2700 K (Warm) Control: Fully dimmable (though a shift to red occurs). The incandescent lamp emits light by reason of its temperature and the Discharge lamp emits light due to an electric current flowing in a gas 2.6) Characteristics:
Low efficacy.General Lighting Service lamp) Lamp Life: 1000 hours.1 Incandescent Lamps Light is emitted from a tungsten filament operating at a very high temperature inside a glass bulb. Advantages: Simple. The temperature of the filament is around 2800K but even at this temperature only about 10% of the energy used is emitted as light in the visible region of the spectrum . vapourisation of the filament occurs as this point is approached and this reduces the life of the lamp. compact. short life. Lamps fall into the general categories of (i) incandescent or (ii) discharge.Lamps and Luminaires 53 ________________________________________________________________________ 2. Disadvantage: High running cost. cheap to install.7 ________________________________________________________________________
Interior Lighting Design . The bulb usually contains an inert gas.1.
very hot operation. 2. 2. 4) more precise beam control 5) Higher colour temperature than GLS. 4) significant colour shift when dimmed. Disadvantages: High running cost.2 Tungsten Halogen Incandescent Lamps These lamps have a tungsten filament and operate on the incandescent principle.H. Advantages: Instant. These lamps are particularly sensitive to a change in supply voltage which affects their operating temperature. cheap to install. Characteristics Efficacy 15-25 lumens/watt (Typically 20 lm/W for a 300W linear lamp) Lamp Life: 2000 hours Colour: Rendering: Excellent (1A) Colour Temperature: 3000 K Control: Fully dimmable (Though a shift to red occurs). excellent colour rendering. The T.g. The addition of halogen gas however. vehicle lights. are sometimes used alongside discharge lamps that require a long warm up time.
Interior Lighting Design . short duration use e. 2) longer life.1.Lamps and Luminaires 54 ________________________________________________________________________ Types of Incandescent Filament Lamp: GLS.8
Applications for Tungsten Halogen Lamps: Security lighting. Reflector. lamps only operate whilst the discharge lamps warm up. Decorative. more than off-sets the ageing effects of higher temperature and as a result.A Student's Guide
.H. They have a higher operating temp (3000K ) which: (i) Increases the efficacy.2. Extra Low Voltage (12V) * * These lamps are commonly referred to as Low Voltage incandescent lamps and have the following advantages: 1) more compact. (iii) Tends to shorten lamp life. 3) increased efficacy. Balanced against this are the problems of: 1) high energy cost. Strip.1. 2) heat dissipation 3) transformers often prove problematic. (ii) Improves the quality of light. Candle. Pygmy. T. the lamp life is doubled.
Characteristics Efficacy: 40-105 lumens/watt Lamp Life:6. Control: The output of HF lamps is dimmable to about 1% light output though the eye may perceive this as greater.V.10
Fig 2.2 LOW PRESSURE DISCHARGE LAMPS 2. 2. radiation is produced when an electric current passes through the gas. Colour Temperature: Depends on lamp colour. good colour rendering. Applications: Commercial and industrial premises.2.000-12. The U.1. U. capacitor Choke L
Interior Lighting Design .F. The inside of the tubes are coated with a combination of phosphor powders.2.V. No shift of colour occurs. long life and almost instant starting. Control gear (ballast) is necessary to initiate the gas discharge and limit circuit current. radiation strikes the phosphor powders and is re-emitted as light in the visible spectrum. Assuming a switching frequency of 8 per 24 hrs. Disadvantages: Efficacy is affected by ambient temp. Colour Rendering: Depends on lamp colour. Max efficacy occurs at 40οC but enclosed luminaires will operate at a higher temperature.Lamps and Luminaires 55 ________________________________________________________________________ 2.000 hrs. The spectral light distribution may be varied by changing the combination of phosphors.
N Fig. Advantages: High efficacy.A Student's Guide
starter lamp P.1 Tubular fluorescent lamps Tubular and compact fluorescent lamps contain low pressure mercury vapour.
Lamps and Luminaires 56 ________________________________________________________________________ High Frequency Fluorescent Lamps The use of electronic control gear operating at 28 kHz approx. Their life cycle cost is much less than GLS lamps when operated for long periods because of the massive savings in energy costs.2.f.2.1. lamps and lamp life increases by about 25%. (compared to the normal mains frequency of 50Hz. (See Fig. Mass production of these lamps as they grow in popularity means their initial cost is reducing dramatically. 2.11
Interior Lighting Design . 2.) improves efficacy by about 10% and allows dimming.
Fig.12). 2. making them even more economical.A Student's Guide
.2 Compact Fluorescent Lamps (CFL’S) CFL’s are being used widely for the replacement of GLS lamps. Flicker is virtually eliminated with h. The use of CFL’s allows greater flexibility in the design of point source luminaires.
These lamps combine a mercury gas tube with a tungsten filament.Lamps and Luminaires 60 ________________________________________________________________________ 2. Advantages: Few compared to SON and metal halide lamps (MBI) which are rapidly replacing them.can be dimmed to 2% of light output with a steady colour. 2.
Interior Lighting Design . They are nonetheless reducing in popularity due to the higher performance of SON and metal halide lamps (MBI).
Fig.2 High Pressure Mercury (MB) Lamps These lamps have been in use since the 1930’s. Characteristics: Efficacy: 40-60 Lumens/Watt Lamp Life: 14000 hrs.A Student's Guide
. Colour Rendering Group: 3 Colour Temperature: 3300K 4000K Control: 5 min run up .2. Applications: Were used widely for street lighting.3. (10-20 lumens/watt).1. The older characteristically blue appearances of the MB lamp has given way to a whiter appearance with the introduction of the MBF (deluxe) lamp which has a phosphor coating. MBT lamps are used where lamp replacement is difficult and where a warm colour appearance is critical. They have a warm appearance. Disadvantage: Lower efficacy than SON or metal halide and poorer colour rendering than metal halide. long life compared to incandescent lamps but a low efficacy compared to discharge lamps.
They are also suitable for use in heat sensitive applications such as food display. offices . Advantages: No specialist skill is necessary to relocate or reassemble the secondary sources.16
Use of Fibre Optic cable Compact metal halide lamps can now be used to provide a primary light source with fibre optic cabling relaying this light to secondary sources. Advantages: High efficacy combined with good colour rendering.A Student's Guide
. The secondary sources may be used in place of low voltage incandescent lamps. factories. commercial interiors. Disadvantages: Warm up time makes it unsuitable for occupancy on/off control.
Interior Lighting Design . Making use of a high efficacy MBI light source has obvious advantages for energy savings. 2. The addition of halides improves the colour rendering to such an extent that they are widely used for sports stadia where good colour performance is important. Characteristics: Efficacy: 70-90 Lumens/Watt Lamp Life: 6000 Hours Colour Rendering: 1A-2 Colour Temperature: 3000-6000 K Control: 2 min run up (5-15 min restarting). They can be located very close to the subject being illuminated. Sparkle is easily provided with jewellery and glass displays and artefacts are conserved because there is no ultra violet or infra red radiation. Dimming to 40% possible but a shift to blue occurs.3. They are used to light security cabinets thereby eliminating the need for relamping.mainly in uplighters. Applications: Stadia. The primary source is located so that the heat produced can be prevented from entering the space being illuminated. The ultra violet and infra red radiation content in the secondary light is negligible.
Fig.3. Metal Halide (MBI) Lamps These lamps have largely replaced MBF lamps because of their improved colour rendering and higher efficacy.2.1.Lamps and Luminaires 61 ________________________________________________________________________
2. 6. For example. Use.1. Waste Disposal
An environmental study within the lighting industry considered items 3 to 6 above in detail as they related to light sources. incandescent lamps are the least efficient and are top of the league with regard to emissions. Similarly the most efficient lamps will produce least emissions in this order: 1. Low pressure sodium (SOX) High pressure sodium (SON) Tubular fluorescent High pressure mercury vapour Compact fluorescent lamps
Note: Metal halide lamps were not considered. CONCLUSION The environmental effects of light sources are mainly determined by the energy consumed during the service period of the lamp. 3. Packaging.g. Production. Transformation into materials.A Student's Guide
. Exploration and extraction of raw materials.
Interior Lighting Design .3 ENVIRONMENTAL EFFECTS OF LIGHT SOURCES The life chain of a lamp includes: 1.Lamps and Luminaires 62 ________________________________________________________________________ 2. For further details see section 5. 5. colour rendering etc. 3. The study concludes that light sources will be rated in reverse order of luminous efficacy. Energy use for all steps of the life chain were calculated along with the emissions involved. 5. The lighting designer should always select the lamp with the highest efficacy consistent with the other requirements of the installation e. 4.11 of CIBSE code for interior lighting. 4. 2.
000 lumens. It is important that this very bright source is shielded from view in order to prevent glare.1 Sulphur Lamps These lamps were invented in 1990 by scientists in America working for the Department of Energy and NASA. 76 lm/W). A significant portion of the input energy is released as heat and dissipation of this heat from such a small source is a problem.e. Present developments use light pipes to spread the light over the area to be illuminated. (i. At the present state of development.4 NEW LAMP DEVELOPMENTS 2.1.A Student's Guide
.1. Lamp life is expected to be 100. a 5900 watt lamp which is the size of a golf ball provides an output of 450. Colour Rendering. Correlated Colour Temperature can be varied between 4000 and 9000 K. The main difficulty is in controlling this large light output from such a small source.Lamps and Luminaires 63 ________________________________________________________________________ 2.4. Good Light quality Ultra violet light content is low and there is no flicker. Efficacy is expected to be 120 lumens/watt when fully developed.000 hours.
Interior Lighting Design .5 Table 2.A Student's Guide
.Lamps and Luminaires 64 ________________________________________________________________________
1. I P stands for "Ingress Protection" The “IP” system .2.2 LUMINAIRES 2. Luminaires provide support. The designation IP 64 means that the luminaire is completely protected from dust and projections of water from all directions.2. 3. It is the latter characteristic that lighting designers are most interested in.2 Material of supporting surface.
2. protection.3 IEC Classification system for enclosures. This standard does not include luminaires for use in hazardous environments. This classification system is specified so as to protect personnel from contact with live or moving parts inside enclosures. The material of the supporting surface for which the luminaire is designed. 2.Lamps and Luminaires 65 ________________________________________________________________________ SECTION 2. Degree of protection afforded against ingress of dust and moisture. The second digit indicates the degree of protection against ingress of moisture.1 Luminaire Constructional Features.1.1. The CIBSE guide “Lighting for hostile and hazardous environments” should be consulted for further information on these luminaires. to prevent the ingress of solid foreign bodies including dust. 2. and to prevent the ingress of moisture.1Protection against shock. Degree of protection afforded against electric shock.
2. The first digit indicates the degree of protection against contact by persons with parts inside enclosures as well as that of the protection against ingress of solid foreign bodies.
Interior Lighting Design . but before considering that let us first consider BS 4533.2.2. and electrical connection to the lamp as well as control of light output.is taken from IEC publication 529. In this standard luminaires are classified according to: 1.g. Materials of the supporting surface are listed in BS4533.A Student's Guide
TABLE 2.4 IP CLASSIFICATION SYSTEM FOR ENCLOSURES
is improved but the glare produced is relatively high.
Opal Diffuser SHR 1. This type of luminaire was very popular in offices in the 1970’s before the use of visual display terminals (VDT’s). the decision facing most lighting designers is whether the luminaire to be selected should have a reflector.75 : 1 or even 2 : 1 is possible with these luminaires because of their “Batwing” light output. The widespread use of VDT’s nowadays precludes the selection of any of the above types of luminaires in modern offices because the glare produced by veiling reflections would be unacceptable. stores. a diffuser or a louvre .F.2. Applications include factories. e.75
Prismatic diffusers refract or bend the light in such a way as to allow luminaires be spaced further apart.A Student's Guide
.and if so which type. Prismatic luminaires are suitable for use where there is little or no use of VDT’s and only moderate glare control is necessary. Bare batten Reflectors are used on suspended SHR 1.g. toilets. Opal white diffusers are used where the limiting glare requirements are low and installation costs are to be minimised. Where VDT’s are used.Lamps and Luminaires 67 ________________________________________________________________________ 2. 2. The light output for each type is shown on the accompanying polar diagrams. A space to height ratio of 1. special low brightness luminaires are required. warehouses etc.17
Interior Lighting Design .00 Fig.
SHR 1. Bare batten fluorescent luminaires would be used where installation cost is be Transverse Axial minimised and glare is not an important factor.2 CONTROL OF LIGHT DISTRIBUTION Notwithstanding all of the above requirements for the luminaire.75
VDT Category 1 luminaire SHR 1.5 luminaires or where dark ceilings would absorb much of the upward light. Let us first consider various types of fluorescent luminaire. The U.
2. The geometry of the viewing angle is irrelevant in uplighting schemes.2 Uplighting Luminaires The light from luminaires is projected onto the room surfaces and reflected light from these surfaces then illuminates the room and working plane.2.8m
Interior Lighting Design . Glare from VDT screens will be acceptable provided there are no sharp contrasts of luminance reflected in the screen.A Student's Guide
.Lamps and Luminaires 68 ________________________________________________________________________ 2. Nonetheless uplighting will normally be about 10% less efficient than downlighting.
1. Uplighting is unsuited for use with occupancy detectors where metal halide lamps are used because their restrike time is high (up to 15 mins).19
Uplighting results in a bright room with walls and ceilings having a non-uniform but nonetheless high luminance. it should be noted that this system allows the use of highly efficient lamps (normally metal halide) and luminaires with an extremely high light output ratio. Although indirect lighting is inherently less efficient than direct lighting.
4.3 MANUFACTURERS' TECHNICAL DATA (for lamps and luminaires)
Each manufacturer will present their technical data in different ways. however.Power in watts.lamp output after 2000h Correlated Colour Temperature . calculation of the new maintenance factor (1994 code) takes account of this change.1B) p42 Colour Rendering Group. This figure is 10 to 15% higher than the Lighting Design Lumen output used in previous codes.Standard. with and without ballast. 2.Colour of lamp expressed as temperature K (See definitions).1A) p42 Physical dimensions. The following terms are commonly used in manufacturers' catalogues: 2. (see table 2.
Interior Lighting Design . There is a wide variety of equipment to meet the different requirements. 1B.Lamps and Luminaires 69 ________________________________________________________________________ 2. Ballast type . The length and diameter of the tube. 1A.lamp output after 100h Lighting design lumen output .
The CIBSE Code for Interior Lighting (1994) recommends the use of the initial lumen output for lumen method calculations.3. Many manufacturers provide computer programs to assist in the design and selection. Information necessary to enable manual calculations is also provided. 3. Colour Rendering Index (Ra) 100 to 0 (see table 2.A Student's Guide
. It may be necessary to select equipment suitable for locations which vary from offices to hazardous areas containing explosive or corrosive substances. Power rating .1 Lamp Data: i ii iii Initial lumen output . low loss or high frequency.
.Lamps and Luminaires 70 ________________________________________________________________________
width and depth. flameproof etc.These include rated voltage.3. Electrical characteristics .This is used as a means of determining the amount of light which will reach the working plane.surface. temperature classification. The information is shown in the form of a polar curve or a table. fire protection.The ratio of the total light output of the luminaire to the light output of the lamp/lamps.This information shows the luminous intensity from different viewing angles in the transverse and axial planes. etc. frequency and safety class. Space Height Ratio .The ratio of the DLOR to the LOR of the luminaire. the light output ratio. Upward light output ratio (ULOR) . Downward light output ratio (DLOR) .2 Luminaire Data: i Light output ratio (LOR) .
Interior Lighting Design . recessed.Lamps and Luminaires 72 ________________________________________________________________________ 2.A Student's Guide
.Length. Utilisation factor .Recommended Spacing to height ratio given in the transverse and axial planes in order to achieve the required uniformity ratios in the task area.These include materials.The ratio of the total output of the luminaire below the horizontal to the light output of the lamp/lamps. air handling. the luminaire mounting height. Downward Flux Fraction . the shape of the room. Physical Dimensions . It is provided in the form of a multiplier and can be extracted from a table. Ingress Protection. Type . Mechanical characteristics .The ratio of the total light output of the luminaire above the horizontal to the light output of the lamp/lamps. the height of the working plane and surface reflectances. Luminous Intensity Distribution . It will depend on the light distribution from the luminaire.
Isolux diagrams can be generated using computer programmes and this will allow the designer establish whether the illuminance variation requirement is met in a particular installation. Co-ordinated design is essential and a compromise with architectural requirements or mechanical services is normal in these situations.
Fig. it is easier to meet this requirement. number and layout of the luminaires. The maximum illuminance is usually at the centre of the room and the minimum illuminance is usually in the corners.7 (ignoring the effects of daylighting). The task area may not include the corners of the room. To this end. Alternatively. in which case.A Student's Guide
.Lamps and Luminaires 73 ________________________________________________________________________ Luminaires should be selected and spaced in a room so as to meet aesthetic as well as functional requirements. the final location of luminaires may be determined by ceiling tile position or location of other services such as ceiling diffusers from the air conditioning system. The illuminance variation is determined by the type. The ratio of maximum to minimum illuminance in the task area should not be less than 0. chart 5 on page 69 can be used as a guide.20 (Cymap drawing)
Interior Lighting Design . 2.
Lamps and Luminaires 74 ________________________________________________________________________
Lamps and Luminaires 76 ________________________________________________________________________ 2.A Student's Guide
).5 Fire Protection The fire behaviour of the mounting surfaces and of the surroundings of the luminaires must be considered when selecting luminaires. they must use luminaires marked F F (limited surface temperatures)
Interior Lighting Design . wood.g. fibres from industry etc. etc.A Student's Guide
. Luminaires marked with F are suitable for direct mounting on surfaces which retain their shape and remain stable at temperatures up to 180 degrees C. to collect on the luminaires.3.Lamps and Luminaires 77 ________________________________________________________________________ 2. plasterboard. (e. If it is possible for highly flammable materials such as dust .
.Lamps and Luminaires 78 ________________________________________________________________________ 2.3.6 Ingress Protection.
2. initial lumen output 5400 lm. (see diagram on page 73)
Interior Lighting Design .75
15. Table 2 indicates that the maximum limiting glare index is 10. design a suitable lighting scheme for an office with the following dimensions: length 10m.9 (16)
3.3.Lamps and Luminaires 79 ________________________________________________________________________ 2. length 14.8m 0.= (10 + 8) 2. which is 50% higher than the office in the example. height of working plane maintenance factor reflectances ceiling walls floors recommended illuminance 0.02
0.95 10 x 8 --------------.7 x 0. the illuminance uniformity requirement will be met. This indicates that the actual glare will be less than the reference glare.85m
2. page 75). (see table 5.4m and height 3m. colour rendering group 1B.2 x 1.9 for the reference room. CCT class intermediate. the dimensions of which are. The illuminance in the reference room is 775 lux.25.2m 1. It follows that this scheme will meet either requirement.75 (nom) 2. width 7.A Student's Guide
. LxW --------------(L + W) Hm = 0. height 3m.7 x 0.2m.5m 2m
The actual SHR is less than 1. It contains 32 luminaires. The recommended maximum limiting glare index is 19 for general offices and 16 for areas with VDT 's.665 (table 4. width 8m. therefore.7 70% 50% 20% 500 lux
Select a 58 W triphosphor fluorescent lamp.7 Using manufacturers' data to design a lighting scheme Using a Trilux luminaire type 5401 RPH/58. page 75)
500 x 10 x 8 --------------------5400 x 0.665 = = = 2.
3 3.Lighting Controls
the peak cooling load will also be reduced.A Student's Guide
. The user feels in control and this is a very important psychological factor in producing user satisfaction. Modern lighting controls operate automatically but should always have a manual over-ride so that users can assert their control when necessary. manual or fully automatic light controls available. so that. to reduce lighting energy costs by 30 to 50 %. taking no account of occupancy.
Interior Lighting Design . by taking account of daylight contribution and reducing the lighting load. will go un-noticed by the user because the eye is able to adapt to the changed illuminance within the dimming period. Luminaires which suddenly switch off are likely to cause annoyance. This may be a critical factor in determining whether or not there is a need for costly air-conditioning systems. improved quality of lighting scheme and the added prestige which results from a high-tech office. maintenance or cleaning. The system will then revert to automatic mode after a pre-determined period. is when all lights in a building are switched on at the start of the working period and turned off at the end. Other significant benefits are: reductions in running costs. effects of lamp ageing. A typical problem situation. The alternative of using fluorescent lamps with high frequency electronic ballasts. A good lighting control system can also be cost effective in installation terms because it does away with the need for costly rewires when alterations in layout occur.Lighting Controls
3. the simple on/off switch is not to be undervalued. It is possible. The challenge for designers is to implement modern cost saving control systems in a user friendly way so that there is no dissatisfaction generated when the controls operate automatically. It should also be noted that the time of maximum daylight contribution is usually the time of maximum direct solar heating gains.1 Introduction: The type of lighting control with which one is most familiar is the simple manual on/off switch. notwithstanding the fact that the illuminance remaining may be well in excess of the minimum recommended design figure. which gradually dim the luminaires so that their output (and power consumption) may be as low as 10% of normal. by using an efficient lighting control system. contribution from daylight. which modern lighting control systems seek to address. Although there now is a choice of remote.
3.5 sq.5 mm 2 size of MCB 6 amp 10 amp nominal power rating 500 Watts 1000 Watts number of points 10 10
Consider the reflected floor plan of a lighting installation shown in Fig.1 The luminaires used are Class 2. mm. square modular.A Student's Guide
. In an open plan office. Practical considerations. mm. mm.1 ________________________________________________________________________
Interior Lighting Design .1
Size of cable 1.Lighting Controls
3. level 1 (50 % lights off) for maintenance and cleaning and level 2 (all lights on) for normal business.5 sq.) which are required in order to comply with the wiring regulations. Table 3. i. with four per circuit or 2.5 sq. They may be supplied by either. such as the size of terminals. 1.
Fig. dictate that lighting circuits may not be supplied by electrical cables larger than 2.5 sq. and 2.2 Circuiting arrangements for Luminaires The luminaires must be properly grouped before they can be properly controlled.5 sq. luminaires adjacent to windows should be on the same circuit. For example. 125 Watt. The following table shows the size of cable. 600mm. the luminaires should be grouped to allow bi-level lighting. mm. suitable for use in an office using VDU's. protective device and nominal power rating of the circuits (60m. cross sectional area.e. mm with eight per circuit. run approx.5 mm 2 2. 3. The sizes normally used are 1.
however. it is common to provide general lighting plus task or localised lighting. a third level of lighting may be required for security. the emergency lighting usually forms an integral part of the general lighting scheme.
Interior Lighting Design . Ideally. L1 + L2 should have their own control so that they may be dimmed or turned off when daylight levels permit while at the same time. however. two switch wires) (L1 L2 L3 L4 L5 L6 L7 L8) + open plan office with daylight control on (L9 L10 L11 L12 L13 L14 L15 L16) window luminaires (two circuits)
It should be borne in mind that offices may be changed from open plan to partitioned.2
partitioned office with daylight control on (L1 L2) (one circuit. The foregoing paragraphs indicate that there is not a single solution that will apply successfully to all situations.A Student's Guide
. In an area such as a factory. This indicates that L1 + L2 should be grouped with L9 + L10.Lighting Controls
Table 3. It is now possible to provide the flexibility required by using lighting control systems in which the luminaires are wired in groups of two to a programmable local control unit which can be stand alone or part of an integrated system. being further from the window. may be left on. Note: The requirements of emergency lighting should be considered separately. Changes to the system can be accommodated by reprogramming the local control unit. Expensive switch drops can be eliminated by using hand held infra red remote units which activate ceiling mounted receivers. Expensive "rewires" were inevitable when new tenants moved into an office block before the advent of modern controls. The same considerations apply to the general lighting as apply to the office area described above. L9 + L10.
sometimes with advanced central control from a building management system.3 Types of Control: The types of control can be divided into two broad categories.c.1 On /Off from single or multiple positions using fixed switches. Automatic Control: (i) Time switch (ii) Occupancy sensors (iii) Daylight sensor (vi) Dimming (v) Reduced voltage 3. This tends to result in all lighting being switched on in the morning.'s Distribution Board Main switch fuse or isolator
Figure 3. left on all day and switched off again by operating the main switch in the evening.
Local switches Luminaires m. the main switch/isolator for the lighting distribution board is used for switching on and off all the lighting with local switching hardly ever carried out in practice. Individually switching up to 20 circuits for a floor in an office block can be very tedious on a daily basis and very often. (iv) Multiple lighting scene control using infra red remote controller. (ii) On /Off using infra red remote controller.b. Many systems have a combination of both. Manual Control: (i) On /Off from single or multiple positions using fixed switches. manual and automatic. (iii) On /Off / dimming from fixed switch position.3.2 ________________________________________________________________________
It should be noted that emergency lighting will require a mains supply at all times in order to keep the standby batteries fully charged and also to prevent the emergency lights from turning on (they are usually triggered on by failure of the mains supply).c.'s Distribution Board Contactor
Figure 3. It is therefore not possible to turn off all lights using the mains switch if emergency lights are on the same distribution board.b. cleaning / maintenance and full occupation. the operating coil of which is controlled by a remote fixed switch (fig 3.3). A typical arrangement would have three such contactors controlling illuminance levels for security lighting.3
Smaller contactors can be clipped on to the DIN rail in the Distribution Board for controlling groups of circuits.
Local switches Luminaires m.
R. ceiling mounted receivers and local control units. Any other changes to wiring required by alterations of layout can be easily accommodated in the false ceilings which are normal in modern offices. however.4
The Local Control Unit is programmable and usually contains automatic control functions as well as the Remote IR on/off functions. receiver false ceiling luminaire
hand held transmitter Fig. 3.
Interior Lighting Design . The luminaires are connected to the output terminals and the control devices are connected to the input terminals. in order to avoid the accidental operation of ceiling receivers other than those intended. 3.4 The IR transmitters are highly directional and of 12m range approx.Lighting Controls
3.3. each office being individually controlled through its own IR receiver. The system layout is as shown in fig.
Structural ceiling local control unit luminaire I. and all receivers may be operated by any transmitter within range.A Student's Guide
. They are not coded. This type of control does away with the need for wiring to switch positions (switch drops) on walls or partitions.2 On /Off using infra red remote controller. This system uses infra red transmitters. Several local units would normally serve a large open plan area. One local unit can serve several smaller offices.
The control is essentially variable voltage control which is carried out electronically using S. fluorescent. group discussions.4 Multiple lighting scene control using infra red remote controller. Fig 3.3. For "passive control". High frequency discharge lamps can be electronically dimmed very successfully to 10% output without colour shift but mains frequency fluorescent lamps are not suitable for electronic dimming. metal halide lamps. video projection and T. viewing. A typical system would have up to 16 pre-set lighting scenes which allows sophisticated lighting effects to be selected instantly to meet specific requirements.A Student's Guide
.V. showrooms.3. The different lighting scenes can be achieved by selective switching or dimming of incandescent. halogen. shop display etc. a control voltage 0 .R 's.10 V D. 3. Most high frequency ballasts have "passive" and "active" dimming control inputs. boardrooms. etc. The system can be expanded to include the control of blinds and projector screens etc.C. such as.C. This is a common arrangement which is used to control the output from luminaires. This system is designed for conference centres. from an external source is used. rotary or slide 10 K potentiometers can be connected to the inputs and for "active control". informal meetings. theatres. auditoria.
Interior Lighting Design .5 shows a typical system layout.Lighting Controls
3. slide and overhead presentations. Incandescent filament lamps lend themselves most readily to dimming although a colour shift is unavoidable.3 On /Off / dimming from a fixed switch position.
hour going backward and forward as the seasons change.25 minutes before turning off when no presence has been detected. This is usually provided by a three position (On/Off/Auto) switch.6 Occupancy sensors for automatic control. It can be anticipated that the running hours life of the lamp will be reduced by using occupancy sensors but this may be more than offset because the lamps will be on for fewer hours in a given period.5 Diagram courtesy of Philips Lighting 3. It can be programmed to take account of working day requirements. All of these devices should have a manual over-ride facility so that they may be turned on or off manually at any time irrespective of the position of the time switch. 3. A person emits infra red radiation at a different level to the background. Many types have a seven day cycle and a back up spring to maintain correct time during mains failure. Occupancy sensors are passive infra red (PIR) movement detectors which activate when they detect a change in the background infra red radiation. An activation produces a change in output from an on-board relay which in turn operates an input in the local control unit. The controls are arranged so that the luminaires will switch on immediately when presence is detected but will delay for a period of 10 . weekends.3.5 Time switch automatic control:
The most common type of timer now used is the programmable timer.3.Lighting Controls Fig 3. Care should be taken that sufficient background lighting is available to prevent danger should the sensors fail to detect presence and turn off. Bank Holidays. The mechanical clock time switch is outdated technology. The life of a lamp is a function of the number of times it is switched on and off. a change of its position in the detection field therefore creates the conditions for an activation of the PIR. The switched outputs of a time switch can be used to control the luminaires directly (up to a certain load limit) or they may control the coil of a main contactor (Fig. in that it is likely to get out of synchronism with real time because of seasonal changes and mains failures. etc. It is important that designers are aware of the safety implications of installing lighting controls which may suddenly turn off.A Student's Guide
. It has severe deficiencies.3. It is a microprocessor with a rechargeable standby battery for memory hold-up and maintaining time in the event of a mains failure.3).
Fig. 180. The PIR units can be mounted on walls or ceilings depending on the application. offices. 90 or 5 degrees field of view.A Student's Guide
. This can be 360. 3. Sometimes more than one detector is required in a given space to ensure adequate coverage.6
An essential part of the PIR detector is the optical lens which determines the detection field. The existing switch can be removed and replaced by the combined unit.
Interior Lighting Design . The units are designed for store rooms. A PIR unit is available which combines as an ordinary switch. corridors etc.
3.Lighting Controls
Ceiling mounted PIR Unit Corner mounted unit plan view Fig.3.7 Daylight sensors for automatic control Inorder to take advantage of daylight it is necessary to introduce the appropriate controls. Daylight linking requires a daylight sensor linked to a controller.7 PIR sensor
Interior Lighting Design . The sensor which is located about 1. 3.8
3.5m from the window. the daylight sensor is directed to the interior and is screened from direct daylight. Contrary to expectations.A Student's Guide
. senses the reflected light from the interior surfaces and modulates the light output from the luminaires accordingly thus constituting a classical closed loop control system.
3. Master / Slave dimming is also possible so that the luminaires furthest from the windows (slave luminaires) are dimmed to a lesser degree.A Student's Guide
DAYLIGHT CONTROL Fig. the amount being determined during commissioning. The luminaires closest to the windows are usually controlled in this way because the greatest benefit is derived in this area (reductions in energy consumption up to 60%.).9
Interior Lighting Design .4 re maintenance factor). When a lighting installation is new. the light output can be as much as 25% higher than design requirements (See section 1.Lighting Controls
3.8 Automatic dimming control.3. It will increase immediately after periodic cleaning and gradually reduce again until the installation is relamped. This will gradually reduce as dust gathers and lamp depreciation takes place.A Student's Guide
12 features a mini control unit and local units connected by means of a two wire communication bus.A Student's Guide
.4 Integrated lighting control systems: These systems are modular in concept and combine all of the control functions previously described. The reduced voltage control system reduces the applied voltage after a time delay by 10 % approximately.
Fig. and the light output by 10%.15% in energy costs at a stroke. It takes a few minutes for normal fluorescents to reach full light output after being switched on.Lighting Controls
illuminance at design values throughout the life of the installation thus saving 12 . This relatively inexpensive system is used in stores and warehouses which are occupied infrequently. This has the effect of reducing the energy consumption by 20% approx. Fig 3.3. Operational features are as follows:
3.11 Diagram courtesy of Philips Lighting 3. An occupancy sensor may be used to switch on to full output when presence is detected. 3.9 Reduced voltage Control.
Lighting Controls (i) (ii)
Centralised management of up to 300 luminaires. In addition to the features described above. (v) Manual control by push button or remote IR unit (vi) Central control from the mini control unit (vii) Programmable timer control for fixed time of day / day of year (viii) Centralised maintenance diagnosis.A Student's Guide
. (iii) Daylight linking of luminaires. (iv) Occupancy control by PIR sensors. 3.
Fig. Local switching pattern that is centrally re programmable to allow for changes in office layout.12 Diagram courtesy of Philips Lighting
Larger units which can be expanded to manage up to 2400 luminaires. the advantages of a full Building Management System can be implemented such as: (i) (ii) Measurement of energy consumption Ability to define more than one user per system Interior Lighting Design .
Interior Lighting Design . 3.
If the Maintenance Factor is 0.000 x 0.= 742. 3. calculate: i The annual energy saving.00.5% Daylight contribution (15%) Total annual saving ii =
12.700 x 0. additional cost ---------------annual savings 1200 ------.000 kWh = £2.A Student's Guide
.700 = 2.75 and the maintenance period is one year. Electrical load = 600 x 20 = Annual energy consumption 12 x 3000 Annual running cost = 36.5 + 405 = 742.5
1. Assume that the light output from the luminaires decreases uniformly over the maintenance period and a 15% saving acrues from daylight contribution.6 years
Interior Lighting Design .5 = 2. Automatic dimming control is used to take account of the Maintenance Factor and daylight contribution.15 = 405 337.12 end Illuminance with automatic controls
i The annual energy saving. The lighting runs for 3000 hours per year and the cost of electricity is 7. The additional cost of installing the dimming controls is £1200.125 = 337.Lighting Controls
Example 3.000 Watts = 36. ii The simple payback period.1 A building has a floor area of 600m2 and a lighting load of 20 W/m2.700 x 0.075 Average reduction over full period is 12.
100% 75% 50% 25% 0 start maintenance period Fig.5 pence per kWh.
1 Introduction Section 4.2 Visual Comfort Section 4.8 Overall Design Section 4.6 Control of Artificial Lighting Section 4.11 Calculation of daylight at a point.SECTION 4
CONTENTS: Section 4.9 Depth of a room Section 4.7 Daylight Control Section 4.4 Energy Cost Section 4.5 Daylight Factor Section 4.
.10 Calculations of average Daylight Factor Section 4.3 Daylight Quantified Section 4.
with supplementary artificial lighting being automatically controlled but with local override facilities provided for staff.A Student's Guide
. Research shows that people value the variety of daylight. Until the 1950’s. DAYLIGHT IN INTERIORS 4. There are 3 reasons to provide daylight: 1. air and noise pollution made it necessary to keep windows closed and provide air conditioning. Sick building syndrome (SBS) was another factor which moved designers away from wholly artificial indoor environments. enjoy the presence of sunlight in a building and want some view of the outside world. 2. Healthier and more satisfactory indoor environment. 3.2 Visual Comfort Daylight is the natural light to which the human eye has become adapted over millions of years. Conserves earth’s resources and improves company's “Green Image”.1 Introduction: No modern analysis of interior lighting would be complete without considering the penetration of daylight into interiors. Economic advantage in energy savings. buildings were designed to allow natural light reach virtually all parts of the building interior. Buildings of the 21st century are likely to rely more on natural daylight. taller deeper plan buildings grew in popularity particularly in city centres where land was extremely expensive.
Interior Lighting Design . In particular colour rendering by daylight is the subjective standard by which we normally measure the colour performance of an electric lamp.
4. Daylight deprivation is a significant factor in people's dissatisfaction with buildings and hence SBS. In addition. The energy crisis of the 1970’s made designers think again.Daylight in Interiors
4. With fluorescent lamp development and cheap energy. In the 1990's public awareness of environmental issues has made engineers even more aware of the importance of conserving energy.
season. this provides psychological benefit and allows our metabolic rhythms to synchronise with the time of day. will provide very good colour rendering.). there are no obstructions (inside or outside) and the window sill is not significantly higher than the working plane. which is approximately the latitude of the British Isles The amount of daylight received within a building depends on its orientation. the variation of daylight may cause difficulties. is likely to cause problems of glare. good modelling is provided by the cross vector of daylight. The natural variation of daylight in intensity and colour over time provides variety and interest in interiors.provided glass is clear. Where exact colour rendering of a colour critical task is necessary however. 4. A minimum of 10 kilolux will be provided for about 70% of the working day at a latitude of 52% N.3 Daylight Quantified Current work on a European daylighting design guide suggests that there will be a necessity for about 30 daylighting design zones for Europe. trees etc. The colour critical task is normally carried out in a test room.Daylight in a building. When side windows are used. coastal or inland location. (Clear glass in high windows however. An outside view provides information on the external climate. climate and air quality. The Building Research Establishment in Britain (BRE) provide information on illuminance due to daylight in London.) It is important to remember that "daylight" is considered to be diffuse light provided by the sky as a whole and not direct sunlight. Daylight varies with latitude. the presence of obstructions and the reflectance of adjacent structures.
. even though it is constantly changing in intensity and colour. It is common practice in the UK and Ireland for lighting designers to use a figure of 10 kilolux for external illuminance when calculating the level of illuminance due to daylight. This shows that mean horizontal diffuse illuminance varies from 35 kilolux at midday in summer to about 10 kilolux at midday in winter . The area in a room to which daylight will be considered to contribute significantly to task illuminance extends to about twice the window height . The term "skylight" is often used instead of "daylight"..assuming an unobstructed sky (buildings. colour matching lamps are used in this case and daylight is excluded. For this reason.
4. Typically. there is a reduction in the mechanical cooling load for the building as well as the electrical load. Care must be taken however. The substitution of daylight for artificial light can produce savings of 30% 70%* if artificial light is well controlled. 5% of 10. Due to the constant variation of daylight. 4. Calculate the illuminance at each of these points assuming an external horizontal illuminance of 10.000 lux. calculations are normally based on a percentage daylight factor. When lighting levels are reduced.4 Energy Cost. automatic control of artificial lighting combined with good daylight penetration may even tilt the balance between the need for air conditioning or natural ventilation for some buildings.000 lux = 300 lux 2% of 10.A Student's Guide
. B and C in an office are 5%.000 lux = 200 lux
Fig. to shield occupants from direct effects of sunlight by providing blinds or other shading devices which can be controlled by occupants. light energy would be between 20% and 50% of the total energy bill.
The cost of energy for artificial lighting is a substantial part of the total energy for most buildings.Daylight in Interiors 4. the air conditioning load is nearly always a cooling load. as part of The Thermie Action Programme.000 lux = 500 lux 3% of 10. Heat generated by artificial lighting contributes to this cooling load.1
The daylight factor at 3 points A.5 Daylight Factor. Daylight factor is the amount of daylight reaching an interior as a percentage of the external illuminance.1
Interior Lighting Design . In some cases. *Source: “Daylighting in Buildings” issued by the European Commission Directorate-General for energy. 3% and 2% respectively. Example 4. In HI-TECH air conditioned offices with widespread use of computers.
Example 4. there is likely to be complaints from staff. 4.2
. Nonetheless in Northern Europe. their tolerance for illuminance and luminance variation is likely to increase. Dimming should operate very slowly in response to increasing daylight. manual switching by staff in the area is acceptable however. 4. because they feel they have control. Automatic switching of lights as daylight levels increase is likely to be annoying to staff. the lighting over point B to 50% output and the lighting over point C to 60% output calculate the total illuminance at A. daylight will normally be supplemented with artificial light for most of the day. If artificial lighting is switched off when the contribution from daylight is less than twice the illuminance provided by artificial lighting. 300 lux at point B and 200 lux at point C. Shadows in the interior and high contrast areas around windows are created which may lead to irritation of staff in that area.
300 B Floor Fig. The lighting over point A is dimmed to 20% output. B and C.Studies have shown that staff react negatively to sudden interruption of artificial lighting. If artificial lighting is reduced to 20% output when daylight levels are high then occupants will have the impression that artificial lighting is “on” and they will not feel any sense of deprivation.6 Control of Artificial Lighting The ideal control system will modulate artificial light levels in each area with the level of daylight.2 Artificial lighting in an office provides an average of 500 lux on the working plane. Daylight provides 500 lux at point A. In this way transient variations in daylight are ignored and people working in the area will not notice the artificial light level decrease. As people become more accustomed to increased daylight in buildings however.
000 per annum.000 x 40% = £2. The installed lighting load is 20 Watts per m2 and operates for 3000 hours per annum. because a 1% improvement in productivity will pay for even a top quality lighting scheme in a short time.a.000 x 100 =
£ 1.500.000 x 10p = £6. It is clear from this that any annoyance to staff must be eliminated for a control system to be of benefit to a company.4% of the salary bill.
Interior Lighting Design . because the total light energy bill is 0. 20 Watts/m2 x 1000 = 20 kW = 60. The annual salary bill for the company.Daylight in Interiors Example 4. Energy costs 10p per kWh.A Student's Guide
.400 per annum.000 p.a. Calculate: (a) (b) (c) (a) The annual light energy bill.000 kWh
Energy consumed per annum = 20 kW x 3000 hrs Cost = 60.000
The benefit of introducing energy control is significant at £2. (c) Salary Bill = £15. The saving if artificial light is reduced to an average of 60% output throughout the year.3
An office area is 1000 m2. It caters for 100 personnel at an average salary of £15. It is equally clear that it is good value to provide a good quality lighting scheme which staff will appreciate. People have become more “green” in their attitude to the use of energy and in general staff do not like wasteful lighting systems. (b) Average Output = 60% Average Saving = 40% Cost benefit = £6.400 p. The benefit must be kept in perspective however. Usually they want a good quality scheme and automatic control with override facilities.
The lightshelf also provides shading from direct sunlight to people close to the window.7 Daylight Control It is necessary to reach a reasonable compromise between ensuring good daylight penetration and reducing the negative aspects of sunlight. How successful it will be will depend on its orientation. One of the aims with an atrium is to reduce space heating load whilst improving daylight penetration into the building. darkened or reflected glass are all useful aids to control daylight. In cities it may be possible to open a window onto an atrium where it would not be possible to open one onto a street because of noise and/or air pollution.7. shades.4. 4. lightducts and transparent insulation are all used to enable daylight to penetrate deeply into buildings. overhangs. Lightwells. High daylight factors enable reductions in light energy costs but glare must be controlled and people must not be subjected to direct sunlight to the extent that their thermal comfort is affected. roof lights.3
. lightpipes.2 Light Shelves
Light shelves are increasing in popularity in modern buildings. Incoming daylight is redirected onto the ceiling improving daylight factor at the inner part of the room.7. An atrium acts as a thermal buffer and windows facing into it may be larger than they may otherwise have been. geometry. roof monitors.1 Atria These are used in modern buildings as inhabited lightwells. lightshelves. Lightshelves are placed at the window above eye level. 4. (See Fig. Blinds. 4. Special consideration of the selection and positioning of display screen equipment is necessary in buildings with large arteas of fenestration (windows) (see chapter 6) 4. internal reflectances and the nature of the roof and glazing.3)
Floor Fig.
Fig.4 Lightpipes and Lightducts Sunlight is collected by heliostats (mirrors controlled by tracking devices). Recent development of thermo hydraulic tracking systems powered by solar cells should improve the viability of these devices in the future. light is cast in a more uniform way. 4.M.A Student's Guide
.3 Roof lights Roof lights are best for daylight penetration whilst minimising heat loss. Light transmission varies from 45% to 80% and it costs about three times the price of double glazing.Daylight in Interiors
4. Horizontal rooflights admit 3 times more daylight than vertical windows of a similar size.5
T. In addition.7. vertical or near vertical roof lights as well as roof monitors or clerestorys are often used instead of horizontal roof lights. The disadvantage of roof lights is that they admit more light and heat in summer than in winter. They are cost effective only in regions where blue skies are guaranteed for most of the year. 4.7. 4. Energy efficient back up lamps may be substituted for sunlight during overcast conditions. 4.5 Transparent Insulation Materials (TIM) These materials are translucent rather than transparent and are used mainly as insulating materials for wall structures. concentrated by means of mirrors or lenses and then directed to the core of the building through shafts or acrylic rods or fibre optic cables.6
Interior Lighting Design . They reduce heat loss from the building whilst permitting solar radiation to reach a heat storing inner leaf. Fig 4.I. For this reason.
and cost less to maintain. size and positioning of any shading device will depend on latitude. A well established rule of thumb for assessing the area in a room which will have acceptable daylight is to determine the "No Skyline Point". however. whilst increasing daylight penetration into the inner parts of the building. All points further from the window are not considered to have acceptable daylight Desks A and B are OK but desk C does not have adequate dayight
Section View Fig. this ensures protection of people near windows from direct sunlight. Internal surfaces absorb the sunlight thus increasing the demand on the cooling system. 4. building orientation and climate. These blinds provide control locally to occupants and they are the most popular choice in Northern Europe.6 Daylight Controlling Devices The type.9
. 4. 4. Adjustable horizontal louvres (venetian blinds) with a specular finish on the upper surface. A building which allows high daylight penetration will also have high solar gains. 4.4.9 Depth of a Room. A saving in artificial lighting energy may be negated by an increase in air conditioning cooling load.7. Interior shades only protect the occupant from direct sunlight and glare. can be angled to redirect sunlight in the same manner as light shelves.9).8 Overall Design Daylight and artificial light must not be considered in isolation to the other energy using aspects of a building. The Architect. External shades are the most effective in reducing heat gains. Internal shades are cheaper. Electrical and heating/ventilating engineers and the rest of the design team must operate as an integrated team producing a comfortable low energy building in which occupants feel they have adequate control of their environment. This is the point at which the skyline is no longer visible (see Fig.
and windows). 4. ceiling.Rb) = = = = Depth of a room Width of a room Height of the window head above the floor Area weighted average reflectance in back half of room (typically 0.+ --W H Where 2 ---------( 1 .7
W Tθ ---. walls. the depth of a room should be limited to meet the following condition: L L -. ceiling.
Interior Lighting Design . and windows). walls.R2) Average daylight factor Window area in m2 (use table to correct for framing) Area of all surfaces in the room in m2 (floor.---------A (1 .A Student's Guide
Fig.5 for an office)
4.Daylight in Interiors
As a general rule of thumb. Glass transmittance (from table) Visible sky angle in degrees average reflectance of (floor.
2 Correction factor for Glass transmission Type of glass Ct Clear 6mm single glazing 0.66 Strongly reflecting 0.small pane 0.46 Tinted Grey 0.large pane 0.18
Table 4.6 Table 4. Cd = Correction factor for dirt on windows. Ct = Correction factor for glazing materials other than clear glazing. Di = Internally reflected component.65 Tinted bronze 0. De = Externally reflected component.6
4.7 Wood frame . Cr = Correction factor for dirt on internal surfaces.large pane 0.8 Wood frame .8 Clear 6mm double glazing 0.9 Metal frame . Computer programmes can calculate daylight factors at various points in a given room with great ease and speed.1 Correction factor for type of frame Type of frame Cg Metal patent glazing 0.11 Calculation of Daylight Factor at a point.7 0. A sample point is normally selected in a room and a calculation is made of the daylight factor at that point. Isolux diagrams of the illuminance throughout the room can be produced once a value of external daylight illuminance is input along with room and window data.3 Location Clean Industrial Very dirty
Correction factor for Dirt on Glass Cd 0.9 0.
. Daylight factor (D) is calculated as follows: D = Cg Ct Cd (Dc + De + Cr Di) Where Dc = Direct sky component.Table 4. Cg = Correction factor for glazing bars which reduce glass area. Daylight factor is quoted as a percentage of the outside illuminance.39 Tinted Green 0.
11.5. Using table 4.4 metres wide.2m Distance from window = 2m Width of window to one side Width of window to other side
.5 An office has a row of desks at cill height 2 metres from a window which is 1. h d W1 W2 = = = = Height of window = 1. (b) On the desk opposite the side of the window. 4.16 of CIBSE Code for Interior Lighting). calculate the direct sky component: (a) On the desk opposite the centre of the window.in Britain) provide a sky component table which is reproduced in the CIBSE code for Interior Lighting (Table 5.16
Example 4.1 Sky Component (Dc)
This is the light reaching a point in a room directly from the sky.
Interior Lighting Design .4m
Fig.Daylight in Interiors 4. The BRE (building research establishment .2 metres high and 2.
1.2 --2
0.2 --.= 0.= ---.9%
Example 4.4 ---2
= 1.6% h 1.6 d 2 W --d 2.= d
1.9% = 190 lux
. Total Direct Component = 1.2 ----.4 when the external horizontal illuminance is 10. (a) (b) 10.000 x 2.000 x 1.= 0.2 Therefore Dc = 1.000 lux.= d W1 ---.6 Calculate the illuminance due to the direct sky component at points A and B in Example 4.3%)
This is the percentage daylight factor from one side of window only.6% = 260 lux 10.3% x 2 = 2.(a)
h --. The benefit from the other side is the same therefore.6 (From Table 2
Dc = 1.
2m. 4.5 d 3 W1 6 --. B and C.2 --.95% + 0.54% = E due to direct sky component at point C = 10.5.7 Calculate the direct sky component and the illuminance due to Dc if external illuminance is 10 kilolux for points A. in Fig 4.000 x 12.5 --.9 B
At point A h = 1. The window is 1.A Student's Guide
.= --. d = 1m.= 2 d 3
Dc = 0.5m h 1. W1 = W2 = 3m h 1.
3.0m A 6.2m high.2 d 1 Dc = 6.95% due to benefit from one side h 1. W1 = 6m.5 d 3 1. W2 = 1.= --.4 d 3 Dc = 0.0m 4.5m 1.96% = 96 lux At Point C h = 1.2m.7.4% = 1240 lux At Point B h = 1.= 0.2 --.= 0.2 --.= --. W1 = 4.2m.2 --.= 1. W2 = W 3 ---.Daylight in Interiors
Example 4.= 0.000 x 0. d = 3m.= 0. d = 3m.5m Plan view Fig.= 1.= ----.= ---.5 --.4 d 3 W2 1.= 3 d 1
0 h 1.= --.2% x 2 = 12.= ---.49% = 149 lux
Interior Lighting Design .= --.000 x 1.0m C 1.4% E due to direct sky component at point A = 10.96% E due to direct sky component at point B = 10.4 d 3 W1 4.49%
Dc total at point C = 0.
RS + R 1.1%
.2m P 0.4m
The examples considered so far have calculated the sky component at cill height opposite some part of the window.2m 1.8
1.6m. PR
h = 1.6 d 1
h 1.= 0.6 --. 4.= 3.8m.= --.2
h = 0.8 d 1 Therefore Dc = 9.8 --. 2. 4.8m 2.8 --. 3.6 --.= 3. d = 1m .10 S 1. Treat these wall areas as though they were windows as follows: 1.6 --.6m Fig.6 d 1
Therefore Dc = 2. Calculate Dc for PQRS Calculate and subtract Dc for PR Calculate and subtract Dc for RS Calculate and add Dc for R
Q = PQRS .= ---.Example 4.8 d 1 Therefore Dc = 7.8 m. PQRS h = 1.= ---. W = 1. W1 = 3. Consider point P in Fig.6m Q R 1.= 1.2 ----1
h 1. W 3.6 1 W 3. RS h --d
1.2m W ---d 1. R and S.= 1. 4.0m 3.8% 3.PR .6m. W = 3. d = 1m. d = 1m. it is necessary to also consider wall areas P.4% 2.8. In order to calculate the direct sky component at point P from window Q.6m.= --. 0.
4.7. W = 1.2 1
h = 0. W --d 1.6m.8 .Daylight in Interiors
4. It is only necessary to calculate De if direct daylight is severely limited by an external structure.4%
.6 d 1 Therefore Dc Dc at P = 1.1 + 1. d = 1m.2% 10
Interior Lighting Design .2 ---.2 Externally Reflected Component (De)
This is the reflected daylight reaching a point in a room from external structures and surfaces.= 1. 1 Then De = 2% x --.9%
= 9.11.= 0. 4.2m.9 that the external structure is restricting the amount of daylight entering the window W.= --.4 .= 0.6 --. In this case it will be necessary to calculate De. It is seen from Fig.9 = 1.11
. (tables 4.85 AW Di = ------------(CRfw + 5 Rcw) A(1-R) Where: W = area of windows.3 Internally reflected component (Di) This is the light reaching a point after reflection from surfaces within a room.11. Angle of obstruction No obstruction 10 degrees 20 degrees 30 degrees 40 degrees 50 degrees 60 degrees 70 degrees 80 degrees Coefficient C 39 35 31 25 20 14 10 7 5
Formulae and Tables supplied courtesy of BRE 4. floors and walls (inc windows) Rfw = average reflectance of floor and walls below the plane of mid height of the window (excluding window wall). the Externally Reflected and the Internally Reflected components and can be calculated as follows: D = Cg Ct Cd (Dc + De + Cr Di) For most buildings. A = area of ceiling.3 page 105) 4.5 Daylight Factor (D) This is the aggregate of the Direct Sky. floor and walls (inc windows) R = average reflectance of ceiling. depending on the obstruction outside (39 is used when there is no obstruction).1. 4.2 and 4. Rcw = average reflectance of ceiling and these parts of the wall above mid height of window (exc window wall) C = coefficient dependent on the obstruction outside the window. Values for C vary between 0 and 39.11. The amount of inter reflected light varies with the distance from the window but the average internally reflected component for side lit rooms is: 0. the direct sky component Dc is the most significant aspect of daylight penetration.4 Correction Factor The same correction factors apply as for the calculation of average daylight factor.11.
------------.5
Calculate: (a) (b) The average daylight factor in the room The daylight factor and the daylight illuminance at a point in the room located 5m normal to the centreline of the window at cill height.52)
3.---------A (1 .7m high.6 Overall average 0.59 %
0.5m x 4m x and is 2.= -----.= 0.4 Upper surfaces 0. Room reflectances are: Lower surfaces 0.8.5m wide located at the centre of the 4m wall.16 Dc = 0.4 d 5
W 1. The cill height is 0.9.000 lux and there are no external obstructions. W Tθ ---.8W Di = ------------(CRfw + 5 Rcw) A(1-R)
Interior Lighting Design .25
A room measures 6.92%
h 2 Dc = --.= d 5 0. The average daylight illuminance in the room Comment on the above results in relation to the design of the artificial lighting as well as its control.R2) 5 0.7 (1 .0.295 x 2 = 0.8 x 80 -----.= 108. It contains one window measuring 2m high by 2. The minimum external horizontal illuminance due to daylight may be taken as 10.= --. The window glass is clear with a transmittance factor of 0.Daylight in Interiors Example 4.25 --.A Student's Guide
4 + 5 x 0.59 + 1.8 x 5 Di = ----------------(39 x 0.36%
1.7(1-0.
1.000 = = 1.6) = 108. When daylight levels are high.5) Total Df at point X = (c) Eav = E point x 0. automatic switching off of artificial lighting would not be recommended for a room where the average daylight factor is less than 5%. Automatic dimming could provide gradual control down to 20% output.95% of 10. Modulation of artificial light will be desirable to reduce energy costs.95% 392 lux = 195 lux
3.92% of 10.0.
8 Section 5.9 Section 5.3 Section 5.A Student's Guide
.6 Section 5.7 Section 5.10 Section 5.Integrated Lighting Design
Section 5.4 Section 5.11
Interior Lighting Design .1 Section 5.2 Section 5.5 Section 5.
Interior Lighting Design . The code should not be thought of as simply a reference to check the recommended illuminances for installations but as a code of good practice in the design of lighting schemes. The design of lighting for a factory will concentrate on the task. Enhance the visual environment. whereas the design of lighting for a reception area in a building will concentrate on visual appearance. To ensure the safety of people using the building. design was based on an average horizontal illuminance with no thought given to vertical illuminance or the quality of the lighting scheme.1 Introduction When designing any interior lighting scheme reference should be made to the “Code for Interior Lighting” issued by the Chartered Institute of Building Services Engineers (CIBSE) 1994. Mood or atmosphere should be considered in all designs. Emergency lighting must be provided in case of power failure in most buildings. The lighting of any interior should fulfil three functions: 1.
Safety is paramount.A Student's Guide
. but most well lit interiors will have sufficient light to ensure safety. Too often in the past. Whether the emphasis will be task oriented or the enhancement of the interior will very much depend on the type of premises considered. 2. the duration of the task and the consequences of any error. Good lighting design involves incorporating all of the above objectives into the design of the scheme. even if it is of less importance than the other criteria. To facilitate the performance of the variety of visual tasks required.Integrated Lighting Design
5. Allowance must be made for age and poor eyesight. 3.
2 Daylight The incorporation of daylight into interior lighting design is desirable for the following reasons: 1.3.
3. will be considered unsatisfactory to most building occupants. Energy costs are reduced if good control of artificial lighting is provided. The natural variation of daylight provides information about the weather and time of day which occupants will deem desirable. account must be taken of the changing spectral composition of daylight with time of day and change of season.
Note: Modern lighting controls allow the simulation of external conditions in interiors where daylight is excluded. Nonetheless these artificial schemes are never as satisfactory to building occupants as a real view of the outside. prevent panic and illuminate hazards which may be dangerous to personnel.
4. If exact colour rendering is necessary however. Not only is illuminance varied with the time of day but so also is the colour appearance of the lamps used.1 Lighting for Safety Hazards must be made visible.
5. Daylight from a window provides a cross vector of light which will improve modelling and provide a desirable vector/scalar ratio. A room which does not provide a view of the outside where one could have been reasonably expected.
2.3 LIGHTING LEVELS
5.A Student's Guide
Interior Lighting Design . In the event of power failure sufficient light must be provided to allow safe escape from the building. Some discharge lamps have a natural colour shift when dimmed and this effect is used to advantage in these schemes. Colour rendering will be improved in most interiors with good daylight penetration.
To enhance an interior. Note: For further information see Section 5.Integrated Lighting Design
5.3 Lighting for Performance of Task The task should be provided with adequate illuminance taking account of age of operatives.3 Mean Cylindrical Illuminance This is the average illuminance over a very small cylinder at a point. Variations of illuminance and accentuation of certain areas or objects may be desirable.3. Experience and judgement will replace calculation and science in this type of design. small areas of strong colour are often necessary to provide visual stimulation in indirect lighting schemes.A Student's Guide
.3. The selection of strong colours for large parts of the interior would be better suited to a direct lighting scheme than an indirect one.3. Indirect lighting reflected from bright coloured interiors would become colour distorted.
Interior Lighting Design . These areas should not be used to reflect light to the interior.2 of the CIBSE Code for Interior Lighting (1994) 5. 5.3. 5.1 Vertical Illuminance The illuminance on a vertical surface can be calculated using the point to point method or for a regular array of symmetrical luminaires: Average wall illuminance = average horizontal illuminance X wall to task illuminance ratio. 5. Notwithstanding this.3. light will normally be varied in colour.2 Scalar Illuminance This is the average illuminance over the surface of a very small sphere at a given point in a room. It is normally closely related to scalar illuminance but it ignores floor reflectance.3.3.3. task difficulty and duration as well as the consequences of error.2 Lighting to Enhance Visual Environment This will depend on the quantity and quality of light as well as surface characteristics and reflection factors. It takes account of all room surface reflectances. Co-ordination with the architect or interior designer is very important here. It should be remembered that the task is not always on the horizontal. level and source.
5. 5.e.200 = 800 lux at an angle of about 30 degrees. The direction of the axis of the sphere which also passes through the source represents the direction of the illuminance vector because there will be a maximum difference of illuminance at opposite ends of this axis.4 Modelling This is the ability of light to reveal shape in three dimensions.A Student's Guide
In the example shown. flow of light predominantly from above and to one side as shown in Fig. 5.2.4.2
In a downlighting scheme the vector will be vertical with the magnitude largely dependent on room reflectances. The best effects are produced by a number of sources.
Fig. See Fig 1.).
The magnitude and direction of light can be described in terms of an illuminance vector.1 Vector Illuminance
light source E max. Light from a predominantly vertical direction will create contrasts and shadow.4.33
Fig. The magnitude of the illuminance vector is the difference in illuminance (E max.
The vector scalor ratio is 800/600 = 1. 5.
Interior Lighting Design . .17 CIBSE code for interior lighting.E min. 5.Integrated Lighting Design
5. Imagine a sphere which is illuminated from one side.
E min. Contrast with the background is also a significant factor. say the scalar illuminance is 600 lux The vector illuminance is 1000 . Strong modelling is achieved by directing light of different intensities from different directions on a subject.
1 Time Variation. It is of course desirable that the general illuminance throughout the interior would be varied to provide variation and interest.3
An average illuminance of 500 lux.7 E max. 5. requiring the eye to adjust. 5.7) Early interior lighting designers felt that a large number of ceiling luminaires providing a uniform illuminance over the working plane would be the most acceptable lighting design in working interiors. Long term variation occurs as a result of light loss due to lamps ageing or dirt accumulating on luminaires or room surfaces. Transient adaptation occurs when a person's field of view changes from one level of luminance to another. The term “shadow free” lighting was introduced. This last factor has already been discussed under “maintenance factor” in section 1.2 to 1.5 Illuminance Variation (space or time) 5. (for recommended ratios.A Student's Guide
. In the short term before adaptation occurs.4.8. E min. Fig.5. 5. otherwise transient adaptation problems may cause discomfort and affect visual performance. The problem with this theory was that it produced a bland
Interior Lighting Design .1 Spatial Variation: Spatial variation means variation of illuminance over a task area or throughout an interior.8 for general lighting schemes where the perception of faces is important. a maximum illuminance of 600 lux directly under luminaires and a minimum illuminance of 400 lux at the mid point between luminaires would be quite acceptable. should be avoided. a discomfort situation may arise. There may be short term variation in illuminance occurring naturally as a result of changing daylight or occurring either manually or automatically by the operation of lighting controls on the supplementary lighting. Variation of illuminance at the task will normally be acceptable provided the spacing between luminaires comply with the manufacturer's recommended Space : Height ratios. > 0. Nonetheless the task should be of a higher illuminance than the immediate surround but there should not be a sharp contrast.5. > 0.8 E Ave.Integrated Lighting Design
The preferred ratio depends on the direction of the vector as well as the purpose and character of the interior. see section 5. As a rule of thumb the preferred range would be from 1.
Excessive variation of room surface luminances however.
With internal lighting design care must be taken to ensure there are no excessively bright sources within the normal field of vision of people using the installation.a ratio of 1. The eye however. the human eye can adapt well and provide a reasonable performance at 0. 5.7 Glare The human eye can adjust from 100. Chaper 6)
Interior Lighting Design . It takes about 90 seconds for the first 70% of that adjustment to occur and a further 15 minutes for the remainder. When moving from a bright exterior to a dark interior. Present thinking suggests that the careful introduction of shadow and sparkle will enhance the appearance of a lighting scheme greatly without affecting task illuminance unduly. Further information on illuminance / luminance variation is contained in section 2. For example. However. Providing a bright reference point in a dark room can lead to glare.1 lux the approximate illuminance provided by moonlight. 5. it takes time to adapt fully from from one lighting level to another. This accounts for the difficulty the human eye experiences when simultaneously coping with different surface luminances . If a bright source is visible to the eye. Most problems with glare in interiors is caused by windows or luminaires either directly or indirectly. Glare from luminaires is reduced by decreasing the luminance of the source. the lens of the eye will close in proportion to the brightness of the source. needs time to adjust to these changes.6 Adaptation It is possible for the eye to adapt to widely varying levels of illumination.000 to 1. ( see special category luminaires.1 lux under moonlight . Special low glare luminaires utilise louvres to shield the lamp from direct view. The source can be direct as in the case of a luminaire or window or indirect. A bright source in an otherwise bright interior may not present difficulty but a bright source in an otherwise dimly lit interior will certainly present problems. Glare can also be caused by excessive contrast such as a dark background coupled with a bright foreground.4 of CIBSE code for interior lighting. With opal and prismatic diffusers the source luminance is reduced by increasing the area of the source.Integrated Lighting Design
uninteresting lighting scheme. a bright day may provide an illuminance of 100.4.000 lux in bright sunlight to 0.the phenomenon known as glare.000.A Student's Guide
. reflected from a working surface such as a display screen. the eye can cope well with a ratio of 200:1. Care must be taken by lighting designers to ensure that bright light sources are not placed in the field of vision.000 lux whilst at night.
4 of the CIBSE guide provides limiting glare indices for most building interiors.2 Discomfort Glare often occurs.
Interior Lighting Design .1 Disability Glare occurs when vision is actually impaired.A Student's Guide
. It can cause eye fatigue. Section 2. 5. It can be the cause of accidents and a serious reduction of visual performance. headaches and other symptoms related to "Sick Building Syndrome".7.3 Glare Index of discomfort The CIBSE code for interior lighting uses a glare index system. Glare can be subdivided into disability and discomfort glare. Glossy magazines and visual display terminals (VDT’s) are common causes of indirect disability glare because of their reflective surfaces.7. after continuous exposure to high background contrast or high source luminance either directly or indirectly from say VDT’s.Integrated Lighting Design
Glare occurs whenever one part of an interior in the field of vision is much brighter than the general interior. 5.7. The most common causes of glare indoors are windows and electric light sources which are seen either directly or indirectly by reflection. 5.6. A task to immediate background ratio of 3:1 and task to general background ratio of 10:1 is recommended by the CIBSE Code for Interior Lighting. This is a numerical index which may be calculated for lighting schemes. This is a more extreme form of glare and is most likely to occur when there is an area close to the line of sight which has a very high luminance.
each containing two lamps with a luminous flux per lamp of 5.18 where H = height of luminaires above eye level (1.2 Total lamp luminous flux correction factor: = 6 log 10(nF) .2
24m Fig 5.1. Using the uncorrected glare index table and the correction factors provided.2m Luminaires are installed at 2m centres as shown in the diagram.500 1m. determine the glare index for the installation for: (i) long view (ii) short view Height correction factor: = 4 log 10H .A Student's Guide
.7 Wall reflectance = 0.5 Floor reflectance = 0.Integrated Lighting Design
Interior Lighting Design .1 A room has the following dimensions: length = 24m width = 16m height = 3.2m) n = number of lamps per luminaire F = luminous flux per lamp Ceiling reflectance = 0.
table 4.A Student's Guide
.11 cibse code
11 = Height correction factor (from (1)) = Total lamp luminous flux factor(from (2)) = Glare index = 15.2 ------21.
Interior Lighting Design . Discomfort glare for specific installations will be prescribed in a unified glare limit rating.3 0 6. discomfort glare is ranked numerically in order of severity.2 ---------= 20.4
Note: If luminaires are turned the other way.Integrated Lighting Design
(i) long view (refer to CIBSE code) x = 8H y = 12H Viewed end-wise.2 Typical limiting glare indices are: Drawing offices (16) General offices (19) Supermarkets (22) Therefore this lighting scheme would only be suitable for a supermarket. 5.2 0 6. the glare index rises to 22. Like the glare index system. the uncorrected glare index from Table 4.A Student's Guide
.5 14.7.11 = Height correction factor (from (1)) = Total lamp luminous flux factor (from (2)) = Glare Index (ii) short view (refer to CIBSE code) x = 12H y = 8H Viewed cross-wise. the uncorrected glare index from Table 4.4 Unified Glare Rating (UGR) System The “Commission Internationale de l’Eclairge” (CIE) have proposed this system to provide an internationally agreed numerical rating.
5. say in a surgery or clinic. These lamps sometimes exaggerate slightly the primary colours but this is welcomed by most people.A Student's Guide
. In addition. people moving from an area illuminated by SON lamps to one illuminated by fluorescent lamps may suffer “colour shift” problems. Reception areas in offices and hotels are examples of this. Where a cool appearance is required.8. The room must have a minimum task illuminance of 500 lux. Where there is a high level of daylight penetrating the interior an intermediate correlated colour temperature (CCT) source should be used. In areas where good colour rendering is necessary and the appearance of the interior is important lamps of group 1B should be used.2 in Section 2) Lamps such as High Pressure Sodium (SON) which has an Ra of 65 may distort some colours. a high CCT source should be used. Note: The higher the correlated colour temperature the cooler the source Table 2. Some interiors require a warm appearance.
Interior Lighting Design . Where the illuminance is less than 300 lux a warm colour is normally preferred.1 Colour Appearance This relates to the colour temperature of the lamp. 2.8 COLOUR PERFORMANCE 5. Note: Lamps in colour rendering group 1A have a CIE colour rendering index (Ra) > 90 Lamps in group 1B have an Ra between 80 and 90 (See Table 2. The inspector or operator must be given time to adapt to the room before carrying out colour critical tasks. Areas surrounding the task must be of weak chroma and medium reflectance. In addition: 1.2 Colour Rendering When exact colour rendering is necessary lamps of group 1 A should be used in a test room which excludes daylight.8.Integrated Lighting Design
Fig. A regular array of luminaires provide an average maintained illuminance on the working plane (see Fig.9. This type of system will normally provide a rather bland “shadow free” lighting installation but great flexibility of work stations is possible as tasks can be moved around.6). Some of the bland effect can be reduced by introducing some sparkle and contrast into the design. Point sources provide sparkle whilst directional or indirect lighting provide contrast.Integrated Lighting Design
5. Localised lighting tends to provide a more interesting design with emphasis placed on the work station. Localised lighting is more efficient with regard to energy costs because of the more efficient use of light.2 Localised Lighting If the location of a particular work area is known then localised lighting can be used to raise the illuminance on this area whilst maintaining general illuminance at a lower level.7
Interior Lighting Design . The main disadvantage of general lighting schemes is their high energy costs because the whole area is illuminated to the highest level of illumination required for the single most difficult task.A Student's Guide
.1 General Lighting
500 lux general Fig.9.9 CHOICE OF SYSTEM
This is probably the most commonly used artificial lighting system. The average general illuminance should be at lease one third of the task illuminance where localised lighting is provided.
5. 5. 5. 5. good maintenance of these schemes is essential.
. Local lighting ensures efficient use of light energy. The light should be positioned to minimise shadows.10 LIGHTING GUIDES Apart from the CIBSE code for interior lighting the student's attention is drawn to the following guides .
5. The eye should be protected from the lamp itself by the use of a “shade”. A desk would typically be illuminated from the left hand side (for a right handed person) so that there are no local task distracting shadows or veiling reflections. but consideration will be given to the choice of lighting scheme for a modern office in the next chapter. Disadvantages are that low wattage lamps are normally less efficient and Fig. Local individual control should be provided. veiling reflections and glare.3 Local /Task Lighting This is the term used for lighting which illuminates a specific individual workstation. 5.Integrated Lighting Design
Interior Lighting Design .8 maintenance costs are generally higher with local lighting. General illuminance should be at least onethird of the local illuminance.all of which are available from the Chartered Institution of Building Services Engineers.9.
It is not possible. with the limitation of space available here. to detail designs for all of the above installations.
.3 of CIBSE code for interior lighting See table 3.3
Table 2.Section 2.3 of CIBSE code for interior lighting See table 3.3 of CIBSE code for interior lighting 3000-4000
1-2 min run-up with 5-15 min restart 5 min run-up and more than 1 min.3 of CIBSE code for interior lighting 1B
Interior Lighting Design Students Guide by Kaokie I. Ling98 viewsEmbedDownloadRead on Scribd mobile: iPhone, iPad and Android.Copyright: Attribution Non-Commercial (BY-NC)List price: $0.00Download as PDF, TXT or read online from ScribdFlag for inappropriate contentMore informationShow less
RelatedInterior Lighting.pdfby Ayman YassinCIBSE Guide Energy Efficiency in Buildingsby Art JamesTraining Lightingby nst_siddiquiCIBSE Concise Handbook.pdfby cem_kamalLED_Posterby jecuzensCIBSE How to Design a Heating Systemby Abdul Wahab HashmiLIGHTING SYSTEM COURSEby ahmed s. NourLighting+by+Designby ilhamdaniahsalehLighting Audit Conceptsby Mayank DubeyLighting_Design_Basicsby masha22clinical opticsby Boom ArchibaldComfort, CIBSEby Phạm Anh TuấnDimming Lflby alexwongks6118Architecture eBook ERCO Handbook of Lighting Designby surabhi kumariThe Human Eye and the Colourful Worldby Arun Arul DavidCIBSEby AA23 AndrewOptics-chapter 1 Studentsby WongXinXinCIBSE Light Levelsby api-3748395Chapter 02by Satish SmartLighting Design Manualby Moustafa NabilNight Visionby Ankush AgarwalInterior.lightingby Sofia RodriguesLumens Per Wattby madbakingLighting Handbookby carlosmandopintoLight-Reflection and Refractionby a7118683LED Lighting Design Guideby FormerruENGL 395 - Technical Descriptionby patrick_n_perrinPresentation 1by api-3716492Similar to INTERIOR LIGHTINGInterior Lighting.pdfCIBSE Guide Energy Efficiency in BuildingsTraining LightingCIBSE Concise Handbook.pdfLED_PosterCIBSE How to Design a Heating SystemLIGHTING SYSTEM COURSELighting+by+DesignLighting Audit ConceptsLighting_Design_Basicsclinical opticsComfort, CIBSEDimming LflArchitecture eBook ERCO Handbook of Lighting DesignThe Human Eye and the Colourful WorldCIBSEOptics-chapter 1 StudentsCIBSE Light LevelsChapter 02Lighting Design ManualNight VisionInterior.lightingLumens Per WattLighting HandbookLight-Reflection and RefractionLED Lighting Design GuideENGL 395 - Technical DescriptionPresentation 1Electrophysiological Properties of Human Ocular ExtramissionCIBSE Swimming Pools

value: This website is an American e-book and audiobook subscription service that includes one million titles.