Home Insulation Cost: Per Square Foot, by Material and R-Value
Insulation is cheap material and expensive access. This calculator prices the insulation itself; the wall work is a separate project.
Estimate calculator
Estimate calculator
Labour is 40%, the middle of the published 30% to 50% band. Removing old insulation adds $1 to $3 per square foot.
Material comparison
| Material | Per sq ft | R-value per inch |
|---|---|---|
| Polystyrene | $0.25 – $2.00 | 4.5 – 5.0 |
| Fiberglass | $0.30 – $1.50 | 2.2 – 3.8 |
| Cellulose | $0.60 – $2.30 | 3.1 – 3.8 |
| Mineral wool | $1.40 – $2.10 | 3.7 – 4.3 |
| Polyurethane foam | $1.00 – $4.50 | 3.6 – 7.0 |
The R-value column is why the price differences exist. Spray foam costs up to fifteen times what polystyrene does per square foot, and delivers roughly the same R-value per inch at the top of its range while also air-sealing.
Fiberglass is the default because it is cheap and easy. It is also the least effective per inch, which matters in a cold climate where the code demands a specific R-value.
Labour is 30% to 50%
That is a wide band and it is entirely about access. In new construction with open walls, labour sits near the bottom. In a finished house it sits at the top, or the job turns into a drywall project.
This is the honest answer to "how much does insulation cost": it depends almost entirely on whether someone has to open your walls.
The cost the quote leaves out
Installing insulation in a finished wall means cutting, removing, insulating and making good. That is drywall, paint and trim — a separate trade and usually more expensive than the insulation itself.
Removing the old insulation first adds $1 to $3 per square foot and is not optional if it is wet or mouldy. New insulation over wet old insulation is money thrown away.
The practical conclusion: do insulation when the walls are open for something else. It is the single best timing decision in home improvement.
Where the money is
| Location | Typical material | Per sq ft |
|---|---|---|
| Attic | Blown-in | $0.50 – $2.30 |
| Exterior wall | Batts or rolls | $0.30 – $2.10 |
| Ceiling | Batts or rolls | $0.30 – $2.10 |
| Roof | Rigid foam | $0.25 – $2.00 |
| Garage | Fiberglass or rigid foam | $0.25 – $2.10 |
| Basement or crawl space | Rigid or spray foam | $0.25 – $4.50 |
Attics are the cheapest place to add insulation and usually the highest return, because heat rises and the attic is the one place you can work without opening a wall.
Basements and crawl spaces cost more per square foot because the material has to handle moisture, which rules out fiberglass.
What it costs in six states
Material does not change at the state line. Labour does. These are the same 2,500 sq ft job priced with six different wage markets.
| State | Labour factor | Low | High |
|---|---|---|---|
| Oklahoma | ×0.79 | $1,292 | $6,091 |
| Kentucky | ×0.84 | $1,322 | $6,244 |
| West Virginia | ×0.92 | $1,360 | $6,442 |
| New Hampshire | ×1.08 | $1,438 | $6,848 |
| New Jersey | ×1.38 | $1,588 | $7,630 |
| Illinois | ×1.40 | $1,600 | $7,693 |
Only the labour line moves. That is a stated limitation of this model, not an oversight.
Frequently asked
Does insulation pay for itself?
In an under-insulated attic, often within a few years. In a wall that has to be opened, the insulation is a rounding error next to the wall work and should be judged as part of the larger renovation.
What R-value do I need?
It depends on climate zone and is set by local code. Cold states require materially more than warm ones, which is why the same house costs different amounts to insulate in different places.
Can I do it myself?
Batts in an open wall or an attic, yes. Blown-in and spray foam, no — thickness and coverage are the whole product, and getting them wrong wastes the material.
Updated October 2026