| Climate Zone | Wood Frame Max U | Metal Frame Max U | Mass Wall Max U | Your Assembly |
|---|
This wall assembly U-value calculator builds a multi-layer wall from a material library, adds the inside and outside air films, and applies a framing correction to return the overall R-value and U-value. Add up to eight layers, set the framing fraction, stud depth, and the stud and cavity insulation R-per-inch, and the tool reports the clear-field path, the framing path, and the combined effective performance.
The overall U-value is what energy codes regulate, so the page also checks your assembly against ASHRAE 90.1-2019 prescriptive limits for all eight climate zones and for wood-frame, metal-frame, and mass-wall categories.
| Quantity | Equation |
|---|---|
| Layer R-value | R‑layer = R-per-inch × thickness (in) |
| Clear-field R | R‑clear = Σ R‑layer (series, incl. air films) |
| Effective R (parallel) | R‑eff = 1 ÷ [ ff ÷ R‑frame + (1 − ff) ÷ R‑clear ] |
| Overall U-value | U = 1 ÷ R‑eff |
Layer resistances add in series for each heat-flow path; the assembly combines the clear-field and framing paths by the parallel-path (area-weighted) method, where ff is the framing fraction. U-value is the reciprocal of the effective R. Air-film and material resistances follow ASHRAE Fundamentals values, and the climate-zone limits are from ASHRAE 90.1-2019 Tables 5.5-1 through 5.5-8 (nonresidential).