Insulation Savings Calculator

About this calculator

Heat loss through a building surface follows Q = A × (1/R) × ΔT, so raising insulation from an old R-value to a new one reduces the heat-loss rate by the difference between 1/R_old and 1/R_new. This calculator multiplies that reduction by heating degree days (HDD) — a standard measure that sums, over a heating season, how many degrees and days the outdoor temperature stayed below a reference point, typically 65°F/18°C — to estimate total heat energy saved, then converts it to therms or kWh and multiplies by your local energy price.

Homeowners weighing an attic or wall insulation upgrade, energy auditors, and contractors quoting insulation jobs use this kind of degree-day-based estimate to put a real annual dollar figure on a project before committing, since R-value alone doesn't tell you what the upgrade is actually worth — a climate with few heating degree days sees far less payback from the same R-value jump than a cold-climate home, which is why building energy codes and programs like ENERGY STAR set different recommended R-values by climate zone.