Insulation R-Value Calculator

Calculate the total R-value of your wall or attic assembly and see if you meet recommended levels for your climate zone.

Assembly Location

Current R-Value (estimate)

Insulation Type to Add

Thickness to Add (inches)

IECC Climate Zone

Results

Visualization

How It Works

R-value measures thermal resistance — how well a material resists heat flow. Higher R-values mean better insulation. The R-value of an assembly is additive: R-13 wall insulation plus R-5 rigid foam sheathing gives you R-18 total. Different insulation materials have different R-values per inch: fiberglass batts provide about R-3.2 per inch, blown cellulose about R-3.5, and closed-cell spray foam about R-6.5. The International Energy Conservation Code (IECC) sets minimum R-values by climate zone. Attics are the most cost-effective place to add insulation because heat rises and attic access is usually easy. Going from R-19 to R-49 in the attic can reduce heating bills by 10 to 20 percent.