HomeMy WebLinkAboutFile Documents.232 E Main St.0132.2018 (116).ACBK
232 E. Main St.
Aspen, Colorado
Non-Vented Roof Assembly Dew Point Calculation
09.05.18
The calculation must show that the temperature of the condensing surface (T interface) is
greater than 41 degrees F at 35% relative humidity.
T(interface) = R(exterior) / R(total) x [T(inside) – T(outside)] + T(outside)
Where:
T(interface) = temperature at the sheathing/insulation interface or the temperature of
the first condensing surface. Must be greater than 41 deg F.
R(exterior) = the R-value of the exterior sheathing
R(total) = the total R-value of the entire assembly
T(inside) = 70 deg F
T(outside) = 19.8 deg F (mean daily temp)
Wood Shingle Roof Assembly:
Thickness:Component:R-Value:
Outside air layer 0.17
5/8”Wood Shingle 1.6
40 mil Ice and Water Shield 0.15
3/4“Plywood Sheathing 0.94
4”Rigid insulation 20
- - - - - - - - - - -condensing surface - - - - - - - - -
3/4“Plywood Sheathing 0.94
Inside air layer 0.65
R(exterior) = 0.17 + 1.6 + 0.15 + 0.94 + 20 = 22.86
R(total) = 22.86 + 0.94 + 0.65 = 24.45
T(inside) = 70 deg F
T(outside) = 19.8 deg F
T(interface) = R(exterior) / R(total) x [T(inside) – T(outside)] + T(outside)
T(interface) = 22.86/24.45 x [70 - 19.8] + 19.8
T(interface) = 66.92 deg F
modif. architecture 1200 west lake street suite 200 chicago, il 60607 312.288.2009
12/26/2018
ACM Roof Assembly:
Thickness:Component:R-Value:
Outside air layer 0.17
6mm ACM Panel 0.86
4”Rigid insulation 20
- - - - - - - - - - -condensing surface - - - - - - - - -
40 mil Ice and Water Shield 0.15
5/8”Dens Deck 0.67
2”Metal Decking 0.00
Inside air layer 0.65
R(exterior) = 0.17 + 0.86 + 20 = 21.03
R(total) = 21.03 + 0.15 + 0.67 + 0.00 + 0.65 = 22.5
T(inside) = 70 deg F
T(outside) = 19.8 deg F
T(interface) = R(exterior) / R(total) x [T(inside) – T(outside)] + T(outside)
T(interface) = 21.03/22.5 x [70 - 19.8] + 19.8
T(interface) = 66.52 deg F
modif. architecture 1200 west lake street suite 200 chicago, il 60607 312.288.2009
12/26/2018