Insulation Savings Calculator

Attic first - heat rises, and most homes have under-insulated attics (current vs IRC target). Walls second, especially in older homes. Basement/crawlspace third. Air sealing should precede or accompany insulation - adding R-value without sealing leaks wastes 30-50% of the benefit. Energy Star recommends R-49 for attics in Zone 5, R-38 in Zone 3.

Attics: blown cellulose (R-3.5/inch, recycled content, easier retrofit) or fiberglass batt (R-3.1/inch, lighter, easier DIY). Walls (existing): dense-pack cellulose or blown fiberglass via small drill holes. Walls (new construction): batt fiberglass or spray foam. Basements/rim joists: closed-cell spray foam (R-6.5/inch, vapor barrier built in). Spray foam costs 2-3x other types but doubles as air seal.

EPA estimates homeowners save an average of 15% on heating/cooling costs by air sealing and adding insulation. On a $2,400/year HVAC bill, that's $360/year. Big-jump attic retrofits (R-19 to R-49) close a larger share of the R-value gap and save more of this calculator's estimate - roughly 12-18% versus single-digit percentages for a smaller top-up. Payback runs longer than the percentage savings alone might suggest: see the next question for realistic ranges.

The federal Section 25C tax credit (30% of materials cost up to $1,200/year for envelope improvements) was repealed by the One Big Beautiful Bill Act (OBBBA) for property placed in service after December 31, 2025, so it no longer applies to 2026+ projects. The HEAR (Home Electrification and Appliance Rebates) program is unaffected: up to $8,000 for households below 80% of area median income (AMI), and up to $4,000 for moderate-income (80-150% AMI) households. Rollout is state-by-state; check your state energy office for current availability.

In cold zones (5-7) it faces the warm interior; in hot, humid zones (1-2) it faces the exterior; mixed zones (3-4) use variable-permeance membranes.

No, not anymore. The credit used to cover 30% of materials cost (capped at $1,200/year), but the One Big Beautiful Bill Act (OBBBA) repealed Section 25C for property placed in service after December 31, 2025. Insulation projects completed in 2026 or later no longer qualify, though the separate HEAR rebate is unaffected.

The IRA's Home Efficiency Rebates program covers up to $8,000 of whole-home retrofits for households below 80% of area median income, and up to $4,000 for moderate-income (80-150% AMI) households.

Reasonable for an attic top-up. For the worked example above (1,200 sq ft attic, R-11 to R-49, $2,200/year HVAC bill), this calculator's own numbers put the installed cost around $1,560 to $3,260 and payback around 6 years with no HEAR rebate. A HEAR rebate improves it dramatically: at the moderate-income tier ($4,000) or the low-income tier ($8,000) the rebate covers the entire job, so net cost drops to zero and payback is effectively immediate. Walls typically take longer than attics because their savings fraction is lower (0.18 vs 0.25) for similar per-square-foot costs. Payback improves further if energy rates rise or you qualify for a rebate.