Attic insulation
Blown-in fiberglass attic insulation, R-51 minimum
We seal the air leaks, fit a baffle at every soffit, then blow fiberglass to R-51, even from wall to wall. Free quote.
Our standard, point by point
Every attic we insulate goes through the same list. It doesn’t get shorter because the house is small or winter is coming.
- Ceiling air leaks are sealed before anything gets blown in.
- A baffle goes in at every soffit, so air keeps coming in under the roof.
- Around the chimney, light fixtures and ducts, we keep the safety clearances.
- The bathroom fan, range hood and dryer are vented outside.
- The attic hatch is insulated and weatherstripped.
- Insulation is blown to R‑51 minimum, at the same depth from one wall to the other, with depth rulers to prove it.
- Your home is protected during the work and cleaned before we leave.
R‑51, and up to R‑60 when there’s room
For its LogisVert rebate, Hydro-Québec requires at least R‑50 over the entire roof. We insulate to R‑51 minimum (RSI 9.0), and up to R‑60 depending on the house, when there’s enough space under the roof.
We work with blown-in fiberglass. It reaches the corners nobody can crawl into and lays down an even layer everywhere. Depth rulers stay planted in it, so you can check the depth yourself instead of taking our word for it.
What a neglected attic does to your house
Heat rises. When the attic insulation is thin, packed down or uneven, the heat goes straight through and you pay for it on every bill. When it escapes through the ceiling, it carries moisture with it: snow melts on the roof and refreezes at the edge as an ice dam, vapour condenses on the roof deck, and mold settles into the wood where nobody sees it.
From downstairs, that looks like an upstairs bedroom that never warms up, thick icicles along the roof edge, a stain on the ceiling. If you think there may be vermiculite in the attic, don’t go up there: read our page on vermiculite removal first.
Last
The fiberglass goes in once the rest is fixed
Air leaks, baffles, ducts, hatch: those come first. Then the fiberglass is blown from wall to wall, up to the mark on the depth rulers.
The day of the work
We lay drop sheets in the house and put on shoe covers before going up. In the attic, the order never changes: air leaks first, then the baffles and ventilation, the ducts vented outside, then the hatch. The insulation goes in last, up to the line on the depth rulers. We clean up before we leave.
How long will it take at your place? We give you the exact time in the quote.
What stays with you
A hatch that closes tight, soffits that let air through and an even layer from one wall to the other, with its depth rulers planted in it. Whenever you go up to the attic, you can read the depth yourself.
If an electrician or a roofer has to work up there later, ask them to put the insulation back the way they found it.
FAQ
The questions we get the most
Another question? Call us at (438) 544-6512
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- How much does it cost to insulate an attic?
- The price depends on the size of the attic, the insulation already up there and what needs fixing underneath. That’s why Isolation Cornerstone starts by coming to see the attic, and the quote is free. What drives the price is explained on our attic insulation cost page.
- Can’t you just add more on top?
- A lot of jobs stop at a fresh layer blown over the old one. If a soffit is blocked or warm air is leaking through the ceiling, the new insulation hides the problem instead of fixing it. At Isolation Cornerstone, we fix that before we blow anything in.
- Do I need to empty the attic, or be home?
- Isolation Cornerstone tells you what to plan for during the visit, based on your house.
- How do I know I really have R‑51?
- Look at the depth rulers. Isolation Cornerstone leaves them planted in the insulation so you can read the depth yourself.
- Do you do a blower door test?
- No, we don’t.
- Do I qualify for the rebate?
- Maybe. LogisVert is for homes heated mainly with electricity, when roof insulation and caulking are done together. The full conditions are on our LogisVert rebate page, and Hydro-Québec makes the call.
Get your free quote
We come look at your attic, measure what’s up there, and the quote is free, with no pressure.
Or call us at (438) 544-6512