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R-49 is the common target for the roof or ceiling in cold and mixed climates. That is about 20 inches of blown fibreglass, 15 inches of blown cellulose, 16 inches of fibreglass batt or about 8 inches of closed-cell spray foam. Air seal the ceiling plane before adding any of it.
Enter the size of the house and what you want insulated. The calculator works out the attic, exterior wall and crawlspace or basement areas from the square footage, prices each at this site's 2026 installed rates, and applies your state's labor index — so you see where the money goes before you call for quotes.
With these inputs:
| Result | Value |
|---|---|
| Estimated total, installed | $8,515 |
| Per sq ft of house | $4.26 |
| Attic, blown-in fiberglass to R-49 | $1,850 |
| Exterior walls, dense-pack drill & fill | $4,565 |
| Crawlspace | $2,100 |
| Attic floor / footprint | 1,000 sq ft |
| Exterior wall to insulate | 1,756 sq ft |
Worked example: a 2,000 sq ft two-story house on a crawlspace. Two stories make a 1,000 sq ft footprint — the attic floor. A 1.5 : 1 rectangle of that size is about 25.8 × 38.7 ft, a perimeter of 129 ft. At 8 ft ceilings over two stories that is 2,066 sq ft of exterior wall, less 15% for windows and doors: 1,756 sq ft. Blowing the attic to R-49 at $1.85 is $1,850; dense-packing the walls at $2.60 is $4,565; the crawlspace at $2.10 is $2,100. Total $8,515, or $4.26 per square foot of house. The walls are the biggest line because there is more wall than attic in a two-story house. Where to start if the budget won't stretch. Air-seal and insulate the attic first: it is the cheapest surface per square foot and usually the worst insulated. Then the crawlspace or rim joists, then the walls. Walls cost more because the insulation goes in through holes drilled from outside or inside and every bay has to be filled. Get the attic and walls quoted separately, and ask each contractor what R-value and material they are quoting, whether air sealing is included and whether old insulation is being removed.
Footprint = floor area ÷ stories; attic = footprint · Perimeter = 2 × (1.5w + w), where 1.5w × w = footprint · Wall area = perimeter × ceiling height × stories × 0.85 (15% windows and doors) · Each surface = area × 2026 installed rate × state labor index
| House and scope | Total | Per sq ft |
|---|---|---|
| 1,200 sq ft ranch, attic only | $2,220 | $1.85 |
| 1,500 sq ft ranch, attic + walls retrofit | $5,570 | $3.71 |
| 2,000 sq ft two-story, attic + walls + crawlspace | $8,515 | $4.26 |
| 2,500 sq ft two-story, everything + basement | $13,571 | $5.43 |
| 2,000 sq ft new build, open walls + attic | $4,923 | $2.46 |
Computed with the calculator above. Rates: attic blown fiberglass $1.85, attic batts $1.60, removal $1.55, wall batts $1.75, dense-pack $2.60, crawlspace $2.10, basement rigid foam $3.10 per sq ft installed.
| Job | Typical range |
|---|---|
| Attic top-up (1,500 sq ft) | $1,500 – $2,600 |
| Full attic removal + re-insulate | $3,200 – $5,400 |
| Whole-house wall retrofit (2,000 sq ft home) | $4,200 – $7,800 |
| Crawlspace encapsulation + insulation | $3,800 – $9,000 |
| Garage conversion insulation | $900 – $2,200 |
| Whole-home spray foam (new build) | $7,500 – $16,000 |
On this calculator a 2,000 sq ft two-story house costs about $8,515 to insulate — attic blown to R-49, walls dense-packed and the crawlspace insulated — at national-average labor. The attic alone on a 1,200 sq ft ranch is about $2,220.
About $5,570 for a single-story 1,500 sq ft house with the attic blown to R-49 and the existing walls dense-packed, or $2,775 for the attic only.
Roughly $1.85 per square foot of house for an attic-only job and $4.26–$5.43 for attic, walls and foundation. Per square foot of surface, installed rates run from $1.55 for removal to $3.60 for closed-cell spray foam.
Often, if they are empty: dense-pack cellulose through drilled holes fills each bay without opening the walls. But it costs more per square foot than the attic and the payback is slower, so do the attic and air sealing first.
Labor is most of an insulation bill, so the calculator multiplies each rate by the state labor index used on this site's state cost pages — from about 0.85 in the lowest-cost states to over 1.4 in Alaska.
Need the whole roof at once? The free roofing calculator works out roof area, squares, shingle bundles, underlayment, drip edge, ridge cap and installed cost from one set of measurements.