Total R-Value of R-13 Batts + R-5 Foam Sheathing Wall
A wall with R-13 batts, R-5 foam sheathing, plus standard drywall and sheathing layers achieves approximately R-18.9 total.
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 total R-value of a common 2×4 wall assembly using R-13 fiberglass batts and R-5 rigid foam sheathing.
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.