What things cost
| Type | Installed, 1,000–1,200 sq ft attic |
|---|---|
| Blown-in cellulose | $1,800–$3,200 |
| Blown-in fibreglass | $2,000–$3,500 |
| Open-cell spray foam | $3,500–$5,500 |
| Closed-cell spray foam | $6,000–$10,000 |
| Related work | Cost |
|---|---|
| Air sealing | $500–$1,500 |
| Soffit baffles | $5–$10 each, 20–40 per attic |
| Insulating the attic hatch | $200–$300 installed |
| Electrical work, if needed | $500–$2,000 |
| Vermiculite removal | $3,000–$8,000 |
Across Ontario most homeowners land somewhere between $1,400 and $5,500 all in, with city ranges reported at $1,500–$4,800 in Toronto, $1,600–$4,500 in Richmond Hill and $1,300–$3,500 in Oshawa.
How much insulation should I have?
The current target for existing Ontario homes is R-60. The Building Code requires R-50 to R-60 for attics in new construction depending on the municipality and heating type.
A rough way to read your own attic: go up with a tape measure. Blown cellulose gives roughly R-3.5 per inch, so R-60 is about 17 inches deep. If you can see the tops of the joists, you are nowhere near it — joists are typically 8 to 10 inches.
The rebate is aimed at exactly this situation: houses at R-12 or less, which is most of the pre-1980 Ontario housing stock that has never been touched.
Air sealing comes first
Insulation slows heat moving through a surface. It does nothing about air moving through a hole. If the attic has gaps around light fixtures, the bathroom fan, plumbing stacks and the hatch, warm moist air from the house pours straight up through them, and adding insulation on top just hides the problem.
Worse, that moist air condenses in the cold attic. It is a common cause of frost on the underside of the roof deck in February and stained ceilings in March.
So air sealing at $500 to $1,500 is not an upsell. It is the step that makes the insulation work. Ask any quote whether it is included, and be suspicious of one that skips straight to blowing material.
Ventilation and baffles
An attic needs to stay cold and dry. Soffit baffles keep the new insulation from blocking the vents at the eaves, which is where fresh air enters.
Blow insulation into an attic without baffles and you can smother the ventilation, which leads to moisture, mould and ice damming at the eaves. At $5 to $10 each they are the cheapest line on the quote and one of the most important.
Do I need to remove the old insulation?
Usually not. Topping up over existing material is normal and is what most jobs involve. Removal becomes necessary when the old insulation is water damaged, contaminated by pests, or is vermiculite — which may contain asbestos and costs $3,000 to $8,000 to remove properly.
If your attic has a grey-brown pebbly material that looks like small stones, stop and have it tested before anyone disturbs it. That is a specialist job, not a general insulation job.
Red flags in an insulation quote
| What you see | Why it matters | What to do |
|---|---|---|
| No air sealing line | Insulation over air leaks underperforms and can cause attic moisture | Ask whether air sealing is included and what it covers |
| No mention of baffles | Blocked soffit vents cause moisture, mould and ice dams | Confirm baffles are installed at every rafter bay with a vent |
| Depth quoted in inches only | Different materials give different R per inch | Ask for the finished R-value, not just the depth |
| Rebate promised without an assessment question | Attic alone qualifies in the simple stream, wider insulation does not | Confirm which rebate stream your plan sits in before starting |
| Vermiculite dismissed | It may contain asbestos and needs specialist removal | Have it tested before anyone disturbs it |
| Bathroom fan venting not checked | A fan discharging into the attic is a moisture problem no insulation fixes | Ask where the bathroom fans actually vent to |
Frequently asked questions
It costs two to four times as much and is usually unnecessary in a vented attic, where blown insulation plus air sealing achieves the target. Spray foam has its place in specific assemblies, not as a default.
It is the step that makes insulation work. Without it, warm moist air leaks from the house into the attic through gaps around fixtures and pipes, causing condensation, frost and stained ceilings.
Not usually. Topping up over existing material is standard. Removal is needed when insulation is water damaged, pest contaminated, or is vermiculite, which may contain asbestos and costs $3,000 to $8,000 to remove.
R-60 is the current target for existing Ontario homes, and the Building Code requires R-50 to R-60 for new construction depending on municipality. In blown cellulose that is roughly 17 inches deep.
Yes. Home Renovation Savings pays up to $1,250 for attics currently at R-12 or less upgraded to at least R-50. Attic insulation alone does not require a home energy assessment first.
Blown-in cellulose runs $1,800 to $3,200 for a typical attic and fibreglass $2,000 to $3,500. Across Ontario most homeowners pay between $1,400 and $5,500 including air sealing and related work.
Sources
- Canada Energy Solution, How much does attic insulation really cost in Ontario, updated 11 March 2026 — canadaenergysolution.ca
- Project Landscaping, The cost of attic insulation in Ontario, 3 June 2026 — project-landscaping.ca
- Home Renovation Savings, official program site — homerenovationsavings.ca, checked 18 September 2026
Prices are published ranges collected on 18 September 2026, not quotes. Rebate terms change — confirm on the program site.
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