Title: How insulation works
Headings: Insulation works by providing resistance to heat flow.
Passive Design
How insulation works
Insulation works by providing resistance to heat flow.
Where heat is lost
R-values
How bulk insulation works
Reflective insulation
Thermal bridges

Content: Thermal bridges
Thermal bridges, also called ‘cold bridges’, are parts of the building envelope where heat can escape more readily because the building material connects – or bridges – both sides of the building envelope. Examples of thermal bridges include: timber or steel framing in external walls that connect to both the interior and exterior faces of the wall
aluminium window frames that do not have a thermal break
gaps in (poorly) installed insulation. One area of thermal bridging with a high impact on performance is timber framing in walls. In one research study, measurements made of 47 new houses found the average content of timber framing in exterior walls (excluding doors and windows) was 34%. This is much higher than the 14–18% generally assumed. You can find out more in ER53 Measuring the extent of thermal bridging in external timber-framed walls in New Zealand . If insulation has simply been installed between joists or studs, the R-value of the building element is likely to be less than the R-value of the insulation used because of the thermal bridging. Thermal bridging can be reduced through correct installation of insulation, and by using insulating features such as sheathing on the outside of studs or using thermal breaks in aluminium glazing. More detail is provided in the pages on roof insulation, wall insulation, floor insulation and windows .