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Community and Q&A

Insulation question

Karina_Canada | Posted in Energy Efficiency and Durability on

Hello, The room above the garage in our house is much colder in winter (we live in Canada) and much hotter in summer than the rest of the house. We would like to insulate the space between the garage ceiling and the room’s floor.

As the house 13 years old we have quite big of a space (drop ceiling ) to work with.

2 different contractors suggested different solutions:
1 – the foam spray (much more expensive option),
2- blown fiberglass.

The contractor says that since we have a drop down ceiling and a lot of space to fill with blown fiberglass it will provide the same R value as 3-4″ of foam. Therefore this cheaper option makes more sense for our home.

I am not completely sure as different websites say that spray foam is the best insulation option. Also, I am concerned that fiberglass may have Phenol formaldehyde that is linked to cancer. Would greatly appreciate your advise as to what insulation option to choose.

Thank you!

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  1. GBA Editor
    Martin Holladay | | #1

    I'm not sure what you mean by a "drop ceiling." Is this a suspended ceiling with removable panels, or a conventional drywall ceiling? A drywall ceiling is preferred, because it provides an air barrier.

    Here is a link to an article that discusses this topic: How to Insulate a Cold Floor.

    All of the fiberglass manufacturers in North America has stopped using formaldehyde binders, so you don't have to worry about formaldehyde in your fiberglass insulation anymore.

  2. user-1072251 | | #2

    Insulation works best when the space is tight - aka "air sealed"; otherwise the insulation is overwhelmed by cold air leaking through. So you need to install something under the blown in insulation - plywood or drywall are two possibilities, tape the joists and make certain that NO air can get into the assembly.

  3. Karina_Canada | | #3

    We have a drywall ceiling, but there is a big space between the garage ceiling and the rooms floor. The contractor offered to make an opening in the drywall and blow fill with fiberglass, tightly. Then to close the opening and tape it. Will the 10-12" of fiberglass be equivalent to 3-4" of sprayed foam or it's a waste of money? Thank you!

  4. GBA Editor
    Martin Holladay | | #4

    The spray foam you describe would have an R-value as low as R-11 (for 3 inches of open-cell spray foam) or as high as R-24 (for 4 inches of closed-cell spray foam).

    The blown-in fiberglass would have a much higher R-value (from R-37 to R-44).

    That said, read my article. A continuous layer of rigid foam on the garage ceiling is still a good idea.

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