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Insulating garage walls and ceiling

Jgr327 | Posted in General Questions on

I have a 20x20ft garage that is attached to the house. 2 walls are attached to the house(which are insulated). The 2 garage doors are insulated, the ceiling and walls are drywall. Above the garage there are bedrooms. The builder lowered the ceiling in the garage. There is a 3ft distance from the 2×4 garage ceiling to the bedroom floors (which are insulated). The house has soffit along the entire front. I would assume there is lots of venting.

I have installed a mr. Heater radiant heater in the garage to cut the cold in the winter for working out there. I would like to insulate the area. I was going to cut an access hatch to blow in cellulose to insulate the ceiling. To insulate the walls I was going to drill 4″ holes at the top of each cavity and blow the insulation down the walls. I checked through a ceiling plug and there is no vapour barrier. I do not want to remove the drywall. Do I need a vapour barrier on the ceiling? Or is by blowing the insulation in the ceiling and walls cause an issue?

Thanks for the help. Hope this made sense. I live in Toronto, Ontario, Canada.

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  1. GBA Editor
    Martin Holladay | | #1

    Q. "Do I need a vapour barrier on the ceiling?"

    A. No.

    Q. "Will blowing the insulation in the ceiling and walls cause an issue?"

    A. No. For more information in installing cellulose, see these two articles:

    How to Install Cellulose Insulation

    Borrowing a Cellulose Blower From a Big Box Store

  2. Jgr327 | | #2

    Thanks. Are you able to explain why I don't need the vapor barrier?

  3. GBA Editor
    Martin Holladay | | #3

    These three articles should explain everything you need to know:

    Do I Need a Vapor Retarder?

    Vapor Retarders and Vapor Barriers

    Forget Vapor Diffusion — Stop the Air Leaks!

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