HomeMy WebLinkAboutDew Point Calc DesignsDEW POINT CALCULATION
JOB NAME: Brown Residence
JOB NUMBER: 16019.00
DATE: 3/7/16
CALCS BY: DRC
DP@ DP@ DP@ DP@ DP@
20%RH 25%RH 30%RH 35%RH 45%RH
30 33 37 41 48
Outdoor design temperature (ODT) 13
Indoor design temperature (IDT) 70
Delta T = IDT -ODT 57
Thermal Resistance of Proposed Roof Assembly
Layer R-value
Outside air layer 0.17
Metal Roofing 0.61
Metal Roof Underlayment 0.00
1/2" plywood sheathing 0.63
3" spray foam insulation (R-6.25/in) 18.75
A: point of condensation analysis
R-19 Batt Insulation 19.00
Vapor barrier 0.00
1 /2" gypboard 0.45
Inside air layer 0.61
R-Total 40.22
R-value atA 20.06
TA= Temperature at point A
TA= IDT -(R-value at A)/(R-Total) •(Delta T) 42
DP A = Dew point at point A (35% RH) 41
Is TA warmer than the DP A? YES
Note: To minimize the potential for condensation problems,
humidity levels within the home must be property controlled
and adjusted based on outdoor temperatures.