R-VALUE CALCULATOR
Estimate the total R-value of an insulation assembly
How R-Value Works
R-value measures a material's resistance to heat flow — higher is better. Total R-value is the per-inch R-value of the material multiplied by its installed thickness. Stacking identical layers adds their R-values together. This tool gives a planning estimate; real-world performance also depends on proper installation, air sealing, and moisture control.
Estimate Your R-Value
DOE Recommended R-Values (Cold Climate)
General retrofit recommendations for existing homes in cold-climate zones (including Vermont). These are guidance, not a determination of code requirements for a specific building.
| Location | Recommended Total R-Value |
|---|---|
| Attic / ceiling | R49 – R60 |
| Exterior walls (cavity) | R13 – R21 (assembly-dependent) |
| Floor over unconditioned space | R25 – R30 |
| Basement / foundation wall | R10 – R15 (continuous) |
| Crawlspace wall | R10 – R15 (continuous) |
Important Notes
- R-values shown are typical published midpoints. Actual per-inch values vary by product, density, and manufacturer.
- Compressing insulation reduces its R-value — do not assume a thicker batt always performs better if it is squeezed into a smaller cavity.
- R-value measures conductive heat flow only. Air leakage, thermal bridging, and moisture can sharply reduce real-world performance.
- For Vermont-specific guidance, see our Insulation Types guide or request a free local assessment.
This calculator is for general planning and educational purposes only and does not constitute professional advice. R-values, material performance, and code requirements vary by product, installation, and location. A professional assessment is required to confirm what applies to your home.