Attic insulation averaged $2,100 in 2026, with most jobs between $1,700 and $2,500 — roughly $1 to $3 a square foot. It is one of the cheapest things you can do to a house, and one of the few where the payback is measured in a handful of years rather than decades.
It is also the job most often done in the wrong order. Adding insulation before sealing the air leaks underneath it is like putting a thicker duvet over an open window.
Cost by attic size
| Attic floor area | Installed cost |
|---|---|
| 300 sq ft | $300 – $900 |
| 500 sq ft | $500 – $1,500 |
| 800 sq ft | $800 – $2,400 |
| 1,000 sq ft | $1,000 – $3,000 |
| 1,500 sq ft | $1,500 – $4,500 |
Cost by insulation type
| Type | Per sq ft | Best for |
|---|---|---|
| Reflective / radiant barrier | $0.50 – $2 | Hot, sunny climates |
| Blown-in (fiberglass or cellulose) | $1 – $4 | Most attics, most people |
| Batts | $2 – $4 | Open, obstruction-free joists |
| Loose fill | $2 – $5 | Topping up existing insulation |
| Spray foam | $2 – $5 | Sealing and insulating in one step |
| Rigid board | $2 – $5 | Walls and roof decks |
For a standard vented attic floor, blown-in is the default and it deserves to be. It flows around wiring, pipes and awkward framing that batts have to be cut around — and every gap a batt leaves is a place heat escapes. A tidy-looking batt job with small gaps performs worse than a slightly messy blown-in one.
Spray foam is a genuinely different product doing a different job. It seals as it insulates, which is powerful, and it is the right answer when the attic is being brought inside the conditioned envelope. It is also far harder to reverse and needs a competent installer — badly applied foam is an expensive problem to remove.
Air sealing comes first
Air sealing costs $250–$750. Skipping it is the most common mistake on this job, and it quietly wastes a large share of what you spend on the insulation itself.
Insulation slows heat moving through a surface. It does nothing about air moving through a hole. Every recessed light, plumbing stack, chimney chase, wiring penetration and attic hatch is a hole, and warm air leaves through them all winter regardless of how deep the insulation on top is.
So the order is: seal the penetrations, insulate the hatch, then add depth. A contractor who quotes insulation without mentioning air sealing is quoting the easy half of the job.
Do you need the old insulation removed?
Removal costs $1–$1.50 per square foot — on a 1,000 sq ft attic that is $1,000–$1,500, which can be as much as the new insulation. It is often unnecessary, and it is sometimes essential.
- Usually you can blow straight over the top. Dry, undamaged existing insulation still works; adding depth on top is cheaper and just as effective.
- Remove it if it is wet or has been. Wet insulation does not insulate and points at a roof leak that needs fixing first.
- Remove it if there are rodents. Contaminated insulation is a health issue, not an aesthetic one.
- Remove it if it is vermiculite. Vermiculite from certain older sources can contain asbestos. Do not disturb it — get it tested.
If a contractor insists on a full tear-out of dry, clean insulation, ask why. Sometimes there is a good reason. Sometimes it is a $1,200 line item that did not need to exist.
What else appears on the quote
| Item | Cost |
|---|---|
| Labour | $1.50 – $3 per sq ft |
| Air sealing | $250 – $750 |
| Old insulation removal | $1 – $1.50 per sq ft |
| Inspection | $100 – $300 (often free) |
Two things worth adding while someone is up there anyway: baffles at the eaves so the new insulation does not block roof ventilation, and an insulated, weather-stripped cover for the attic hatch. Both are small money and both are commonly missed.
The bottom line
Budget $1–$3 per square foot, or about $2,100 for a typical attic. Blown-in over the existing layer, with air sealing done first, covers most houses well.
Of everything on this site, this is among the cheapest jobs with the fastest return — and it is worth doing before you replace heating equipment, not after. A properly insulated house needs a smaller system, and sizing the new one against a leaky attic means paying for capacity you did not need.
Which is exactly the argument in our HVAC replacement guide — get the load calculation done on the house you will have, not the one you have now. If solar is also on the list, the payback maths is here.
Anything that penetrates the roof plane changes your insulation detailing — see skylight installation costs in 2026.
Working out your own number? Our free renovation cost calculator gives you the range for your size and area in about ten seconds.