Attic Insulation Calculator

Attic Insulation Guide

Attic insulation is the single highest-ROI energy efficiency upgrade for most homes. Heat rises -- in winter, an under-insulated attic lets heated air escape through the ceiling. The Department of Energy estimates that proper attic insulation can reduce heating costs by 10-50% depending on the current insulation level and climate zone.

Target R-values for attics: R-30 in mild climates (DOE zones 1-3), R-38 to R-49 in moderate climates (zones 4-5), and R-49 to R-60 in cold climates (zones 6-8). Tacoma, WA is in zone 4 -- target R-38 to R-49.

If your attic already has some insulation, measure its depth and estimate the current R-value (fiberglass batts: about R-3.2 per inch). Then calculate how much to add to reach your target. You can layer unfaced batts perpendicular on top of existing insulation.

The Bottom Line

Free attic insulation calculator. Batt packages and blown-in bags by attic area and target R-value. Measure your project area carefully, add your waste factor, and use this calculator to get the material quantity before heading to the supply yard. Accurate estimates save money on bulk delivery charges and prevent mid-project shortages.