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user-7066100 | Posted in Energy Efficiency and Durability on

I have an attic that is not insulated. The attic is over the garage and the garage is insulated .

I want to insulate the attic, my question is:

Do I have to insulate the garage ceiling? I wouldn’t think so?

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  1. GBA Editor
    Martin Holladay | | #1

    User 7066100,
    First of all, can you tell us your name? (I'm Martin.)

    You wrote, "the garage is insulated." This phrase can mean different things to different people.

    Here at GBA, "the garage is insulated" usually means, at a minimum, that the garage walls are insulated and the garage ceiling (or roof) is insulated. It may also mean that the garage slab is insulated.

    But we don't know what you mean when you write that the garage is insulated.

    If you know, please tell us. Is there any insulation in the ceiling of the garage (that is, the floor of the attic)?

    If you don't know, you should look. You may have to drill a hole in the ceiling, or in the attic subfloor if there is one, to figure out if this assembly is insulated.

  2. GBA Editor
    Martin Holladay | | #2

    User 7066100,
    Once you have assessed the current situation, we can move on to a discussion of your plans.

    You wrote that the garage is insulated. Why? Is it kept heated in the winter and cooled in the summer?

    What are your plans for the attic? Do you plan to keep the room above the garage heated and cooled?

    Finally, will both spaces be heated and cooled all the time? Or will these two spaces be heated and cooled at different times?

  3. user-7066100 | | #3

    Hi my name is Jean..

    I will be more specific. Prior owner did not finish with the insulation.

    I have a double size garage walls are insulated, ceiling is not. Garage ceiling is only a sub flooring. Door from the garage leaves to a mudroom, ceiling is not. In mudroom there are stairs leading to the attic, which has no insulation and only the sub flooring. I was going to put a door and walls from the mudroom to the attic and heat the mudroom, with a rinnai heater. So my question is:

    If I just insulate the attic would this keep in the heat in mudroom and attic...I would eventually put a heater in the garage My first winter here and want to see how cold the garage gets..

  4. GBA Editor
    Martin Holladay | | #4

    Q. "If I just insulate the attic, would this keep in the heat in the mudroom and attic?"

    A. If you want to heat a certain area, the need to (a) define the thermal boundary, and (b) make sure that this thermal boundary has an air barrier, along with insulation in direct contact with the air barrier.

    If your goal is to heat the mudroom and the attic, then you would want to install insulation in the attic floor (also known as the garage ceiling), the attic gable walls, and the attic roof assembly.

    If your goal is to heat the mudroom, attic, and garage, then you would want to install insulation in the attic gable walls and the attic roof assembly. You would also want to make sure that the insulation work in the garage walls was complete, and that you have installed vertical insulation (rigid foam) at the perimeter of the garage slab.

  5. user-7066100 | | #5

    Thank-you Martin

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