Total R-Value of a Standard R-13 Wall (No Extra Foam)

A basic 2×4 wall with only R-13 batts, standard sheathing (R-0.45), and drywall (R-0.45) reaches approximately R-13.9 total.

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How to use this tool

Enter the R-value for each insulation layer (set unused layers to 0).
Include sheathing and drywall R-values for a complete assembly calculation.
The result shows total R-value and U-factor for the wall or ceiling assembly.

Calculate the real total R-value of the most common residential wall assembly: R-13 fiberglass batts in a 2×4 stud wall.

Frequently asked questions

What does R-value mean?: R-value measures thermal resistance — how well an insulation layer resists heat flow. Higher R-values mean better insulation. Values are additive when layers are stacked.
What is U-factor?: U-factor (or U-value) is the inverse of total R-value (U = 1/R). It measures heat transfer rate — a lower U-factor means better insulating performance.