The cost to insulate a house depends on which parts you're insulating, not on the home's total square footage. Insulation is priced per square foot of each area that gets work:
- the attic floor
- the wall area (minus windows and doors)
- the crawl space floor
- the garage ceiling or walls
Each area and material has its own installed price per square foot, and extras like insulation removal and air sealing are added on top.
For planning, our insulation cost calculator uses installed-price ranges from about $0.80 to $5.00 per square foot, depending on the area and material. For example, adding blown-in fiberglass to a 1,500 sq ft attic works out to roughly $1,500 to $3,800 using those ranges. A whole-house project that includes walls, removal, or spray foam costs considerably more.
These numbers are for planning only. The real price comes from measuring your home and checking what's already there, which is what an estimate does.
How Insulation Pricing Works
Every insulation price is built the same way:
Area × installed price per square foot = insulation cost
Then extras are added where they apply:
- Insulation removal, priced per square foot, when old insulation is wet, contaminated, or damaged
- Air sealing, often a flat range for a typical attic
The area is measured differently depending on where the work is:
- Attic: the attic floor area, length times width. Spray foam at the roofline is still planned per attic floor square foot in our calculator, but it's installed on the larger roof surface.
- Walls: each wall's length times height, minus windows and doors.
- Crawl space: the crawl space floor area.
- Garage: each ceiling or wall being insulated.
Insulation Price Per Square Foot
These are the planning ranges our calculator uses, based on published installed-price data for the San Antonio market, checked September 2026. They include material and labor. They aren't quotes.
| Area | Material | Planning range (per sq ft) |
|---|---|---|
| Attic | Blown-in fiberglass | $1.00 to $2.50 |
| Attic | Fiberglass batts or rolls | $1.00 to $3.00 |
| Attic | Blown-in cellulose | $1.00 to $2.50 |
| Attic | Spray foam (roofline, per attic floor sq ft) | $2.00 to $4.50 |
| Walls | Fiberglass batts (open walls) | $0.80 to $2.60 |
| Walls | Blown-in fiberglass (existing walls) | $1.75 to $3.50 |
| Walls | Dense-pack cellulose (existing walls) | $1.75 to $4.20 |
| Walls | Spray foam | $1.50 to $4.50 |
| Crawl space | Fiberglass batts or rolls | $1.00 to $2.00 |
| Crawl space | Spray foam | $2.00 to $5.00 |
| Garage | Fiberglass | $1.50 to $4.00 |
| Garage | Spray foam | $2.50 to $5.00 |
| Add-on | Planning range |
|---|---|
| Insulation removal (attic or crawl space) | $1.00 to $2.00 per sq ft |
| Attic air sealing, typical job | $250 to $1,200 |
Example Estimates
Using the ranges above, rounded to the nearest $100:
- Attic top-off, 1,500 sq ft, blown-in fiberglass: about $1,500 to $3,800
- Same attic plus air sealing: about $1,700 to $5,000
- Same attic with old insulation removed first: about $3,000 to $6,800
- Existing walls, 1,200 sq ft, dense-pack cellulose: about $2,100 to $5,100
- Crawl space, 1,000 sq ft, fiberglass batts: about $1,000 to $2,000
- Garage ceiling, 400 sq ft, fiberglass: about $600 to $1,600
Your numbers depend on your measurements, and each area adds up separately. The insulation calculator runs this math for your own measurements and shows a range for the material you pick.
What Changes the Price
- How much insulation goes in. A higher target R-value means more depth, more material, and more labor. Topping off an attic that already has some insulation costs less than insulating a bare one.
- Existing insulation condition. Dry, sound insulation can usually stay, and new insulation goes on top. Wet, moldy, pest-damaged, or contaminated insulation may need removal first, which is often the biggest add-on.
- Access. Low attics, tight crawl spaces, and attics crowded with ducts take longer.
- Open vs. closed walls. Batts in open framing cost far less than dense-packing insulation into finished walls through drilled holes.
- Material and method. Spray foam costs more than blown-in fiberglass or cellulose, and closed-cell foam costs more than open-cell.
- Prep and safety work. Rafter vents at the eaves, dams around flues and non-IC lights, and hatch sealing all add small amounts to the scope.
Where to Start in a Whole House
ENERGY STAR calls the attic the easiest place to add insulation, and it's usually the lowest cost per square foot. It's also where air sealing does the most, since many of a home's hidden leaks sit under the attic insulation.
A common order for a San Antonio home:
- Attic. Seal the air leaks, then bring the insulation up to a consistent depth. Our attic insulation service starts with measuring what's already there.
- Walls. These matter most during a remodel, when the framing is open, or in older homes with empty wall cavities. See our wall insulation service for what's involved in existing walls.
- Crawl space or garage. These depend on the home. A garage with a bedroom above, for example, is worth a look.
What a Good Quote Should Include
- The area measured for each part of the house
- The material and the target R-value or installed depth
- Whether air sealing is included, and what it covers
- Whether any removal is included, and why
- Prep work such as rafter vents, dams around lights and flues, and hatch treatment
For blown-in jobs, the Federal Trade Commission's R-Value Rule requires the receipt to list the coverage area, initial installed thickness, minimum settled thickness, R-value, and number of bags used. That's how you confirm what was installed.
Why Quotes Can Differ So Much
Two quotes for the same house can use different materials, different target depths, or different scopes. One might include air sealing and hatch work while the other doesn't. Comparing total price only works when the scope is the same. Compare R-value, area, and what's included line by line.
Frequently Asked Questions
Is insulation priced by the square footage of my house?
No. It's priced by the area being insulated. A 2,000 sq ft single-story home might have close to 2,000 sq ft of attic floor, but a two-story home of the same size has a smaller attic and much more wall area.
What's the cheapest part of a house to insulate?
Usually the attic floor with blown-in fiberglass or cellulose. It's accessible, fast to install, and uses the lowest-cost materials in our planning ranges.
Does old insulation always have to be removed?
No. Dry, sound insulation usually stays, and new insulation goes on top. Removal is for insulation that's wet, moldy, contaminated, pest-damaged, or in the way of the planned work.
Is air sealing included in insulation prices?
Not always. It's often quoted separately. Ask specifically whether the price includes sealing the top plates, plumbing and wiring holes, recessed lights, flues, and the hatch.
The Takeaway
The cost to insulate a house is the sum of each area you insulate:
- Area times its installed price per square foot, plus removal or air sealing where they're needed.
- Most homes start with the attic, which is usually the least expensive place per square foot and the easiest to improve.
Use the insulation cost calculator to get a planning range for your home, then Get an Estimate for a price based on real measurements and conditions.
References
- ENERGY STAR: A Do-It-Yourself Guide to Sealing and Insulating with ENERGY STAR. energystar.gov
- Federal Trade Commission: Labeling and Advertising of Home Insulation (R-Value Rule), 16 CFR Part 460. ftc.gov
Pricing note: the per-square-foot ranges above are the planning ranges used by the San Antonio Insulation Pros insulation calculator, based on published installed-price data for the San Antonio market, checked September 2026. They're estimates, not quotes, and are updated as pricing changes.