lib/measures/tbd/resources/psi.rb
def glazingAirFilmRSi(usi = 5.85)
  # The sum of thermal resistances of calculated exterior and interior film
  # coefficients under standard winter conditions are taken from:
  # https://bigladdersoftware.com/epx/docs/9-5/engineering-reference/
  # window-calculation-module.html#simple-window-model
  #
  # These remain acceptable approximations for flat windows, yet likely
  # unsuitable for subsurfaces with curved or projecting shapes like domed
  # skylights. Given TBD UA' calculation requirements (i.e. reporting only, not
  # affecting simulation inputs), the solution (if ever used) would be
  # considered an adequate fix, awaiting eventual OpenStudio (and EnergyPlus)
  # upgrades to report NFRC 100 (or ISO) air film resistances under standard
  # winter conditions.
  #
  # For U-factors above 8.0 W/m2.K (or invalid input), the function will return
  # 0.1216 m2.K/W, which corresponds to a construction with a single glass layer
  # of thickness 2mm & k = ~0.6 W/m.K, based on the output of the models.
  #
  # The EnergyPlus Engineering calculations were designed for vertical windows
  # - not horizontal, slanted or domed surfaces.
  unless usi && usi.is_a?(Numeric) && usi > TOL
    TBD.log(TBD::DEBUG,
      "Invalid U-factor, can't calculate air film resistance - skipping")
    return 0.4216
  end
  if usi > 8.0
    TBD.log(TBD::WARN,
      "'#{id}' U-factor > 8.0 W/m2.K - using airfilm RSi of 0.1216 m2.K/W")
    return 0.1216
  end

  rsi = 1.0 / (0.025342 * usi + 29.163853)                        # exterior ...

  if usi < 5.85
    return rsi + 1.0 / (0.359073 * Math.log(usi) + 6.949915)    # ... + interior
  else
    return rsi + 1.0 / (1.788041 * usi - 2.886625)              # ... + interior
  end
end
##
# Returns total air film resistance for fenestration (future use)
#
# @param [Float] usi A fenestrated construction's U-factor in W/m2.K
#
# @return [Float] Returns total air film resistance in m2.K/W (0.1216 if errors)
Returns total air film resistance for fenestration (future use)
Returns total air film resistance for fenestration ( future use )
def glazingAirFilmRSi(usi = 5.85)
   These remain acceptable approximations for flat windows, yet likely
   unsuitable for subsurfaces with curved or projecting shapes like domed
   skylights. Given TBD UA' calculation requirements (i.e. reporting only, not
   affecting simulation inputs), the solution (if ever used) would be
   considered an adequate fix, awaiting eventual OpenStudio (and EnergyPlus)
   upgrades to report NFRC 100 (or ISO) air film resistances under standard
   winter conditions.
   For U-factors above 8.0 W/m2.K (or invalid input), the function will return
   0.1216 m2.K/W, which corresponds to a construction with a single glass layer
   of thickness 2mm & k = ~0.6 W/m.K, based on the output of the models.
   The EnergyPlus Engineering calculations were designed for vertical windows
   - not horizontal, slanted or domed surfaces.
  unless usi && usi.is_a?(Numeric) && usi > TOL
    TBD.log(TBD::DEBUG,
      "Invalid U-factor, can't calculate air film resistance - skipping")
    return 0.4216
  end
  if usi > 8.0
    TBD.log(TBD::WARN,
      "'{id}' U-factor > 8.0 W/m2.K - using airfilm RSi of 0.1216 m2.K/W")
    return 0.1216
  end
  rsi = 1.0 / (0.025342 * usi + 29.163853)                         exterior ...
  if usi < 5.85
    return rsi + 1.0 / (0.359073 * Math.log(usi) + 6.949915)     ... + interior
  else
    return rsi + 1.0 / (1.788041 * usi - 2.886625)               ... + interior
  end
end
def glazingAirFilmRSi ( usi = 5.85 ) unless usi && usi . is_a? ( Numeric ) && usi > TOL TBD . log ( TBD :: DEBUG , "Invalid U-factor, can't calculate air film resistance - skipping" ) return 0.4216 end if usi > 8.0 TBD . log ( TBD :: WARN , "'#{id}' U-factor > 8.0 W/m2.K - using airfilm RSi of 0.1216 m2.K/W" ) return 0.1216 end rsi = 1.0 / ( 0.025342 * usi + 29.163853 ) if usi < 5.85 return rsi + 1.0 / ( 0.359073 * Math . log ( usi ) + 6.949915 ) else return rsi + 1.0 / ( 1.788041 * usi - 2.886625 ) end end
Returns total air film resistance for fenestration (future use)
Returns total air film resistance for fenestration ( future use )
# The sum of thermal resistances of calculated exterior and interior film # coefficients under standard winter conditions are taken from: # https://bigladdersoftware.com/epx/docs/9-5/engineering-reference/ # window-calculation-module.html#simple-window-model # # These remain acceptable approximations for flat windows, yet likely # unsuitable for subsurfaces with curved or projecting shapes like domed # skylights. Given TBD UA' calculation requirements (i.e. reporting only, not # affecting simulation inputs), the solution (if ever used) would be # considered an adequate fix, awaiting eventual OpenStudio (and EnergyPlus) # upgrades to report NFRC 100 (or ISO) air film resistances under standard # winter conditions. # # For U-factors above 8.0 W/m2.K (or invalid input), the function will return # 0.1216 m2.K/W, which corresponds to a construction with a single glass layer # of thickness 2mm & k = ~0.6 W/m.K, based on the output of the models. # # The EnergyPlus Engineering calculations were designed for vertical windows # - not horizontal, slanted or domed surfaces. # exterior ... # ... + interior # ... + interior
Returns total air film resistance in m2.K/W (0.1216 if errors)
Returns total air film resistance in m2 . K / W ( 0 . 1216 if errors )
Float
usi
usi A fenestrated construction's U-factor in W/m2.K
usi A fenestrated construction ' s U - factor in W / m2 . K