Attic Insulation Cost & Savings Calculator
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Runs entirely in your browser — your numbers never leave this page.
How it works
Heat rises, and an under-insulated attic is a chimney for your money — the Department of Energy attributes roughly 25–35% of home energy loss to poor attic insulation. Going from R-11 to R-38 can cut that slice dramatically.
R-value measures resistance to heat flow: higher is better, but returns diminish. The jump from R-11 to R-38 saves far more than R-38 to R-60, which is why R-38/R-49 is the sweet spot for most climates.
Blown-in cellulose is the value pick for topping up existing insulation. Spray foam costs 2–3x more but air-seals at the same time — worth it if your attic leaks air around pipes, wires and the hatch. Always air-seal first; insulation slows heat, it does not stop drafts.
Frequently asked questions
How do I know my current R-value?
Measure insulation depth: fiberglass batts are ~R-3.2 per inch, blown cellulose ~R-3.5 per inch. 3–4 inches of old batts ≈ R-11; 6 inches ≈ R-19. If you can see the joists, you are under-insulated.
What R-value should I target?
R-38 for most US climate zones, R-49 for cold northern states. Check the DOE zone map — going beyond the recommendation has rapidly diminishing returns.
Blown-in vs batts vs spray foam?
Blown-in (~$1.50–2/sq ft) is cheapest and fills gaps well — best for topping up. Batts (~$2–2.50) suit open accessible attics. Spray foam (~$4–5) air-seals too but costs 2–3x; ideal for leaky old attics.
How fast does it pay back?
Typically 2–5 years when upgrading from R-11 or less — among the fastest paybacks of any home improvement. From R-30 to R-49 the payback stretches to 7–12 years.
Should I air-seal before insulating?
Yes, always. Seal gaps around plumbing stacks, wiring, recessed lights and the attic hatch with caulk or foam first. Insulation without air-sealing leaves up to half the savings on the table.
Can I DIY blown-in insulation?
Yes — home centers rent the blower free with enough bags. It is a dusty weekend job for two people. Spray foam is not DIY-friendly; hire a pro.
Does insulation help in summer too?
Absolutely — it resists heat flowing down into living space. In hot climates, attic insulation plus a radiant barrier can cut cooling bills 10–15%.
Will this affect my roof ventilation?
It must not block soffit vents — install baffles to keep airflow from eaves to ridge vent. Trapped moisture rots roof decking, which costs far more than the insulation saved.
Are there tax credits or rebates?
The federal 25C credit has covered 30% of insulation costs (up to $1,200/yr) in recent years, and many utilities offer rebates. Check current DSIRE listings before you buy.
How long does attic insulation last?
Fiberglass and cellulose: 20–30+ years if kept dry. Spray foam: lifetime of the house. If yours is older than that or compressed/wet, replacement beats topping up.