Roof R-Value Calculator

Calculate total thermal resistance of a roof assembly including air films, roofing membrane, insulation, and deck.

Winter: 0.17, Summer: 0.25
h·ft²·°F/Btu
Built-up roof: ~0.33, single-ply membrane: ~0.05
h·ft²·°F/Btu
Polyiso: R-5.6 to R-6.5 per inch, XPS: R-5 per inch
h·ft²·°F/Btu
Steel deck: ~0, concrete: ~0.08 per inch, wood: ~1.25 per inch
h·ft²·°F/Btu
Acoustic tile: ~1.0, drywall: ~0.45
h·ft²·°F/Btu
Heat flow up: 0.61, heat flow down: 0.92
h·ft²·°F/Btu

Results

Total Roof R-Value-h·ft²·°F/Btu
Roof U-Factor-Btu/(h·ft²·°F)
References: ASHRAE 90.1 - Energy Standard for Buildings, ASHRAE Fundamentals Ch. 27