Thermal Resistance (R-value) Calculator
Single Layer R-value
Calculate R-value from material thickness and conductivity
Composite Wall R-value
Add up R-values for a wall assembly
Formula
R = Thickness x R-per-inch | R_total = R1 + R2 + ... | U = 1/R
Frequently Asked Questions
What is R-value?
R-value measures thermal resistance - how well a material resists heat flow. Higher R-value means better insulation. R-values are additive for layers in series.
What R-value do I need?
It depends on climate zone and location in the building. Walls typically need R-13 to R-21, attics R-30 to R-60, and floors R-13 to R-30. Check local energy codes.
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