HomeMy WebLinkAboutFile Documents.517 Park Cir.0161.2018 (18).ARBK David Johnston Architects
517 Park Circle
Warm Roof Worksheet 4.16.18
Proposed Assembly at 70 degrees F-Interior Temperature
January Mean Daily Temperature-Aspen 19.8 degrees F
Thermal Resistance of Assembly
Enter project-specific values in highlighted cells below.
Thickness Component R-Value Standard Material R-Values
Outside air Layer 0.17
Roofing 0.5 Shingles=0.21
Waterproof Membrane 0.21
5/8" Plywood 0.77
4" Closed Cell Spray Foam(R-6.5/1 26 EPS=R4/in.,XPS=R5/in.,Polylso=R6.5/in.
5.25" Batt Insulation 21
5/8"Gyp. Ceiling Material 0.56 5/8"Gyp=0.56,3/4"Hardwood=0.71
Inside Air Layer 0.65
Total R-Value 51.84
Sheathing/Insulation Interface Temperature=(70)-[((R-Value)/(R-Value Total)x(Change in Temperature)]
70 0.68 0.56 21 51.84 50.2
22.24
0.429012
21.53642
Sheathing/Insulation Interface Temperature 148.463581degrees F (compare to chart below)
Temperature of Sheathing/Insulation interface must be above dewpoint for a given relative humidity.
Dewpoint at 30%Relative Humidity 37 degrees F
Dewpoint at 35%Relative Humidity 41 degrees F
Dewpoint at 40%Relative Humidity 45 degrees F
Dewpoint at 45%Relative Humidity 47 degrees F
Dewpoint at 50%Relative Humidity 49 degrees F
Notes:
1 Rigid insulation to be EPS T&G,two layers @ 1 1/2"thick w/overlapping joints in both directions.
2 Cavity insulation may be fiberglass batt,blown in cellulose or other insulation approved by the architect,
however,the cavity insulation value shall not exceed R-30!
3 In order for the warm roof system to work on the coldest night of the year,the relative humidity in the house must be kept to an
absolute maximum of 30%! DJA recommends a design safety factor which would allow the humidity to be no
more than 25%.
4 Due to the low slope of some of the roofs,Ice&Water Shield will be used as the waterproof membrane. Ice&Water Shield is a
membrane impermeable to water and air. Therefore,the roof system is designed to dry to the interior. Any moisture
that enters the system from the interior must also exit to the interior. For this to be possible,there must not be a vapor barrier
on the underside of the roof assembly. The 5/8"gypsum board at the ceiling will act as a vapor diffusion retarder.
This works best if a vapor diffusion retarding paint is applied.
5 Adequate ventilation is key to the performance of this roof assembly. Excess moisture must have a means of being exhausted
from the interior. A slight negative pressure is desired in the house. The mechanical engineer or
design/build subcontractor may design this exhaust as part of the overall air distribution system.
Another simpler way to achieve this slight negative pressure is to install an exterior vented range hood and
put the the bathroom fans on timers so they run for a few minutes each time they are used.
RECEIVED
06/12/2018
ASPEN
BUILDING DEPARTMENT