Most homeowners in Montreal, Ottawa, and Gatineau pay between $2,500 and $5,500 to insulate an average attic in 2026, while a full job that includes removing old insulation and replacing it runs closer to $4,000 to $8,000. The final number depends on your attic size, the material you choose, and whether there is old or contaminated insulation that has to come out first. Below is a clear breakdown so you know what to expect before you call anyone.

Cost by Job Type

The job you actually need has the biggest effect on your bill. There are three common scenarios.

New insulation (adding to a bare or under-insulated attic) is the cheapest path, usually $1.50 to $3.00 per square foot. Insulation removal on its own typically costs $1.00 to $2.50 per square foot, and the price climbs when there is rodent waste, water damage, or mold involved. A full replacement, which means hauling out the old material and installing new, combines both costs and lands most homes in the $4,000 to $8,000 range.

If your existing insulation is wet, packed down, or contaminated, removal is not optional. You can read more about that process on our attic insulation services for Montreal and Ottawa page.

Cost by Material

Material choice changes both the upfront price and how the attic performs over the years.

• Blown-in fibreglass: Lowest cost, fast to install, good for topping up. Roughly $1.50 to $2.50 per square foot.
• Blown-in cellulose: Slightly higher cost, better at filling gaps and resisting air movement. Roughly $2.00 to $3.00 per square foot.
• Spray foam: Highest cost by a wide margin, but seals air leaks and adds the most R-value per inch. Often $4.00 to $7.00 per square foot.
• Batts (fibreglass or mineral wool): Budget friendly for accessible attics but leaves more gaps. Roughly $1.50 to $3.00 per square foot.

Cost by Attic Size

Square footage scales the whole project. A small attic of about 600 square feet might cost $1,800 to $3,500 for new insulation, a 1,000 square foot attic often lands between $2,500 and $5,000, and a larger 1,500 square foot space can reach $4,000 to $8,000 or more. Add removal on top of those figures if old material has to go.

Regional Differences in Montreal, Ottawa & Gatineau

Pricing across the three cities is fairly close, but a few things shift the numbers. Montreal labour rates tend to sit a little higher than Gatineau. Ottawa pricing usually falls between the two. Older homes in central Montreal and the Outaouais often have harder attic access, which adds labour hours. Available rebates also differ, since Quebec and Ontario run separate energy programs, and those can take a real bite out of your net cost.

What Affects the Price

Beyond size and material, these factors move your quote up or down: attic accessibility and ceiling height, the depth of insulation you want, whether ventilation or air sealing needs work, and the condition of what is already up there. The single biggest surprise cost is contamination. If a technician finds mold or rodent droppings, the attic usually needs cleaning before any new insulation goes in. Our attic decontamination service for Montreal and Ottawa covers that step.

FAQ

How much does it cost to insulate an attic in Ottawa?

For an average home, expect $2,500 to $5,000 for new blown-in insulation. Spray foam or a full removal and replacement will push that higher.

Is it worth removing old attic insulation?

Yes, when the old material is wet, compressed, moldy, or contaminated by pests. Otherwise you can often top up what is already there.

How much does attic insulation removal cost?

Most removals run $1.00 to $2.50 per square foot, with contaminated attics costing more because of the extra cleaning and disposal.

What is the cheapest attic insulation?

Blown-in fibreglass is usually the lowest cost option and works well for adding to an existing layer.

Are there rebates for attic insulation in Quebec and Ontario?

Both provinces offer energy efficiency programs that can reduce your cost. The specific grants and amounts differ between Quebec and Ontario, so check current programs before you book.

How long does attic insulation last?

Blown-in insulation can last 20 to 30 years or more if it stays dry, but moisture, pests, or settling can shorten that and signal it is time to replace.