Duct Insulation R-Value Calculator

Calculate required duct insulation thickness to meet energy code requirements and prevent condensation.

1=Unconditioned attic, 2=Vented crawl, 3=Unheated basement
Temperature of air in duct
°F
Temperature around duct
°F
RH in space around duct
%
Code minimum: R-6 to R-8 depending on climate
h·ft²·°F/Btu

Results

Ambient Dew Point-°F
Condensation Risk-
Required Insulation Thickness (R-4.2/in)-inches
References: ASHRAE 90.1 Section 6.4.4 - Duct and Plenum Insulation, IECC Section R403.3