How Much Does Attic Insulation Cost?
By the HomeLintel Editorial Team · Reviewed 2026-08-24
Insulating a typical attic with blown-in fiberglass or cellulose costs $1,500–$5,500 — around $2,800 for most homes — at roughly $1.50–$3.50 per sq ft to reach modern R-values. It is consistently among the highest-return energy upgrades a house can get.
The order of operations matters more than the material: air sealing before insulating. Blown insulation over unsealed attic bypasses — top plates, wire and pipe penetrations, recessed lights, the attic hatch — filters air instead of stopping heat. Sealing first ($350–$1,500) is what makes the insulation perform to its rating.
Cost by approach
| Item | Typical range | Notes |
|---|---|---|
| Air sealing (first, always) | $350 – $1,500 | Foam/caulk at penetrations, hatch weatherstripping, baffles. |
| Blown fiberglass (to R-49) | $1.00 – $2.50 /sq ft | The standard top-up; settles little, resists moisture. |
| Blown cellulose (to R-49) | $1.20 – $2.80 /sq ft | Denser, better air-blocking, recycled content. |
| Batts (DIY-friendly) | $0.80 – $2.00 /sq ft | Only as good as the fit; gaps gut performance. |
| Spray foam roofline conversion | $4 – $8 /sq ft | Creates a conditioned attic; a different, bigger project. |
| Old insulation removal (if needed) | $1 – $2 /sq ft | For rodent contamination or moisture damage — not routine. |
How much R-value you actually need
ENERGY STAR climate guidance: southern states target attic R-30–R-49; the middle of the country R-38–R-49; northern states R-49–R-60. Translation for inspection day: if you can see your ceiling joists, you're underinsulated everywhere in America — joists disappear around R-19. Topping up from R-19 to R-49 is the classic high-return move; going from R-49 to R-60 in a mild climate is diminishing returns.
What you'll actually save
ENERGY STAR's long-standing estimate: air sealing plus attic/crawl insulation saves an average of about 15% on heating and cooling costs — several hundred dollars a year for typical bills, meaning the standard blown-in project pays back in roughly 3–7 years and then keeps paying. Homes starting from nearly nothing (pre-1980, never upgraded) beat those numbers; already-decent attics see less.
Blown-in vs spray foam: different projects
Blown-in on the attic floor keeps the attic cold and vented — cheap, effective, standard. Spray foaming the roofline converts the attic into semi-conditioned space — the right call when HVAC equipment and ducts live up there (common in the South), but at 3–4× the cost it's an equipment-protection strategy, not a first-dollar efficiency move. If your ducts are in the attic, get quotes both ways; if not, blown-in wins the value contest almost every time.
Frequently asked questions
How much does it cost to insulate a 1,500 sq ft attic?
Blown fiberglass or cellulose to R-49: roughly $1,800–$4,500 including basic air sealing. Spray foam roofline conversion for the same attic: $8,000–$15,000+.
Is attic insulation worth it?
It's among the best-returning home upgrades: ~15% average heating/cooling savings per ENERGY STAR when paired with air sealing, comfort gains you feel immediately, and ice-dam prevention in cold climates. Payback typically 3–7 years.
Can I add new insulation over old?
Yes — dry, uncontaminated old insulation stays, new blows over it (unfaced only; no vapor barriers between layers). Removal is only for rodent contamination, moisture damage, or knob-and-tube wiring underneath that needs addressing.
What is the best insulation for an attic?
For attic floors: blown cellulose or fiberglass — performance is similar; installation quality and depth matter more than brand debates. For rooflines with attic ductwork: closed-cell or open-cell foam by design. Batts are fine DIY where joist bays are regular and accessible.
Related resources
Sources & methodology
- ENERGY STAR — Insulation (Rule Your Attic) — R-value targets and 15% savings estimate
- US DOE — Insulation — materials and climate zones
Cost ranges are HomeLintel editorial estimates built from the listed sources and our published assumptions — they are not quotes. Last reviewed 2026-08-24. See how we estimate costs.