Short answer
Most of Canada should aim for attic insulation of about R-50 to R-60, which works out to roughly 14 to 17 inches of blown cellulose or 18 to 24 inches of blown fibreglass. If your attic has less than about R-30, a top-up is often one of the better-value upgrades you can make, especially after air sealing.
Key takeaways
- Target about R-50 to R-60 in most of Canada; milder coastal BC can do well near the lower end.
- Blown cellulose gives roughly R-3.5 per inch; blown fibreglass roughly R-2.5 to R-3.
- Measure your current depth with a ruler to estimate your existing R-value.
- A blown-in top-up typically costs about $1.50 to $4 per sq ft of attic floor.
- Air seal the attic floor before adding insulation, and keep soffit vents clear.
The right attic insulation R-value for most Canadian homes is about R-50 to R-60. That is the level most energy advisors and many provincial programs aim for, and new homes in colder regions are built close to it. Many older homes have R-12 to R-30, which is often a single layer of batts or a few inches of loose fill that has settled over the years.
R-value measures how well a material resists heat flow. Higher is better. Because warm air rises, the attic is where a poorly insulated home loses a lot of heat. Topping it up is usually simpler and cheaper than insulating walls, and it pays back faster in colder parts of the country.
Recommended attic insulation R-values in Canada
Provincial building codes set minimums for new construction, and these vary by climate zone. For an existing home, the following targets are a practical guide.
| Region | Typical target | Notes |
|---|---|---|
| Coastal BC (Lower Mainland, Vancouver Island) | R-40 to R-50 | Milder winters; returns flatten sooner |
| Southern Ontario, southern Quebec, Maritimes | R-50 to R-60 | Common program target |
| Interior BC, Prairies, northern Ontario and Quebec, Newfoundland | R-60 | Colder climate makes the extra depth pay off |
| Far north | R-60 or more | Check local code and program rules |
Going from R-12 to R-50 makes a big difference. Going from R-50 to R-70 makes a small one. Each extra inch saves less than the one before it, so past about R-60 you are usually spending money for very little return.
How deep is R-50 or R-60?
Depth depends on the material. These are typical settled values for loose-fill insulation blown into an open attic.
| Material | Approx. R per inch | Depth for R-50 | Depth for R-60 |
|---|---|---|---|
| Blown cellulose | About 3.5 | About 14 to 15 in | About 17 in |
| Blown fibreglass | About 2.5 to 3.0 | About 17 to 20 in | About 20 to 24 in |
| Fibreglass or mineral wool batts | About 3.0 to 4.0 | About 13 to 17 in | About 15 to 20 in |
Manufacturers print a coverage chart on each bag showing the minimum settled depth for each R-value. Ask your installer to put depth markers on the trusses so you can check the result.
Estimate your current R-value
Go into the attic with a flashlight and a ruler. Measure the depth in several spots, away from the hatch. Multiply by roughly 3 for most loose fill or batts. Eight inches of old fibreglass is likely around R-20 to R-25. If you see grey-brown, pebble-like granules, that may be vermiculite, which can contain asbestos. Do not disturb it. Have it tested and handled by a professional.
Cellulose vs fibreglass
- Cellulose is made mostly from recycled paper treated for fire and pests. It is denser, resists air movement a little better and gets to a target R-value in less depth.
- Blown fibreglass is lighter, does not absorb moisture as readily and does not settle as much over time. It needs more depth for the same R-value.
Both work well when installed to the right depth over a well-sealed attic floor. Pick based on installer experience, price and what is already in your attic. You can blow either material over existing insulation as long as the old layer is dry and free of mould or pests.
What attic insulation costs
Blown-in attic insulation in Canada typically costs about $1.50 to $4 per square foot of attic floor, depending on how much depth you are adding, access and your region. For a typical 1,000 to 1,200 sq ft attic, a top-up to R-50 or R-60 often lands somewhere around $2,000 to $5,000. Removing old insulation, adding baffles, sealing pot lights or dealing with vermiculite adds to that.
Doing it yourself with rented equipment from a hardware store can cut the cost, but attic work is hot, dusty and easy to get wrong around vents and wiring. Most people hire it out.
Rebates
In Ontario, the Home Renovation Savings Program offers up to $7,700 for insulation, and an energy assessment may be required. See Ontario rebates. Other provinces, including programs like CleanBC Better Homes, Efficiency Manitoba, Efficiency Nova Scotia and NB Power, have offered insulation incentives. Check rebates in your province and confirm current amounts before you book. Many programs require an EnerGuide home evaluation first.
Do these things before and during the job
- Air seal first. Seal top plates, wiring holes, plumbing stacks and the attic hatch before insulation goes in. See air sealing first.
- Keep ventilation open. Install baffles at the eaves so insulation does not block soffit vents. A ventilated attic stays cold and dry, which helps prevent ice dams and moisture problems.
- Protect hot fixtures. Older pot lights and chimneys need proper clearance or approved covers.
- Insulate and weatherstrip the hatch. An uninsulated hatch is a cold spot and an air leak.
Is it worth it for you?
If your attic is under about R-30 and you live anywhere colder than coastal BC, a top-up is usually worth it. If you already have R-40 or more, the extra savings are small and your money may do more elsewhere. Run your numbers in the home energy estimator, and read why winter bills are higher to see how heating fits into your total.
Frequently asked questions
What R-value should my attic be in Ontario?
Most of southern Ontario should aim for about R-50 to R-60. Northern Ontario benefits from going to R-60.
How many inches of blown-in insulation do I need for R-60?
About 17 inches of blown cellulose or roughly 20 to 24 inches of blown fibreglass. Check the coverage chart on the bag for the exact settled depth.
How much does it cost to top up attic insulation in Canada?
Blown-in insulation typically costs about $1.50 to $4 per square foot of attic floor. A typical attic top-up often lands around $2,000 to $5,000.
Can I add new insulation on top of old insulation?
Yes, as long as the old insulation is dry, free of mould and pests, and is not vermiculite. Seal air leaks in the attic floor first.
Is cellulose or fibreglass better for an attic?
Both work well at the right depth. Cellulose reaches a given R-value in less depth, while blown fibreglass settles less and is lighter.
Want numbers for your own home?
Use the household energy estimator with your province's prices and climate. It takes about two minutes.