Attic Insulation

jjfriscoAugust 2, 2005

I have a one-story house with an attached garage. The house has soffit vents and attic fans for ventalation. The attic over the house portion seems adequately insulated, but there is no insulation over the garage portion of the attic.

I'm in TX and the garage is on the west side of the house. Is there a reason for the garage not being insulated, other than saving the builder $$$, and would it be beneficial to insulate the attic over the garage?

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since the garage is probably not heated or cooled, there is no real reason to insulate it. if it is heated or cooled then you should have insulation above it.

    Bookmark   August 2, 2005 at 2:01PM
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Thanks. It's not heated or cooled, so that makes sense. Does the same hold true for the attic door insulation that you see?

    Bookmark   August 2, 2005 at 3:04PM
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I agree with the preceding...presuming that the wall that separates the house from the garage is insulated.

    Bookmark   August 2, 2005 at 9:28PM
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Insulaing the garage ceiling could make it cooler in the summer. And of course it might make it warmer in the winter, but not much so. But I'd have to say a cooler garage in summer might be worth it.

    Bookmark   August 3, 2005 at 2:17AM
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Does the same hold true for the attic door insulation that you see?

Is your attic door inside the house or in the garage?
If it is in the garage don't bother, but if
it is in the conditioned space insulate &
Lots of air infiltration & heat gain through
attic stairs & doors!

    Bookmark   August 3, 2005 at 11:39PM
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I agree with spamb. It really depends how you use your garage. If it's just to park your car out of the weather, or store stuff, then maybe not. We have a small workshop area in ours, and also do car maintenance, and having the garage insulated makes it a lot more comfortable to work in.


    Bookmark   August 7, 2005 at 2:09PM
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We live in a newly constructed house with two bedrooms partially over an unheated garage. I know the builders put insulation in because I saw them do it, but both rooms are freezing in the winter and warm in the summer. Our HVAC guy has suggested more insulation above the garage.
Any thoughts?

    Bookmark   January 29, 2006 at 11:21AM
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It's likely not possible to install more insulation in the garage ceiling below the habitable rooms.

These joist spaces should already be filled with the maximum amount of insulation that can be placed in them.

Adding additional insulation below the drywall ceiling is likely not practical because it would require lowering the existing garage ceiling to allow for more insulation.

Foam insulation panels are not an option because the garage ceiling has to maintain fire separation between the living space above and foam insulation is highly flammable.

You would do better to add insulation in the attic of the room above, better seal all cracks to prevent airflow, or consider heating and cooling the garage istself.

    Bookmark   February 1, 2006 at 7:30AM
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You could rip down the drywall take out the fiberglass insulation fill the space between the joists with foam board, I would use the foil faced type. That stuff is rated at R-7 per inch. Then cover it up with 5/8" fire rated drywall.

    Bookmark   February 1, 2006 at 5:28PM
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I have a 15 yr old 2200 sq ft ranch with an uninsulated garage (22X22). Our bedroom is directly behind the garage, sits over a heated crawlspace, and is exposed to 2 outside walls plus the garage wall. The bedroom freezing in the winter. Although the garage is not heated, my mind keeps saying that insulating it will keep the attic warmer. But then I realize that there are vents in the attic, and that it is probably not much warmer than the outside temperature. Looking at this thread, it appears that there is little if any benefit in insulating a garage. Can you clarify the theory of attics and insulation? Thanks!

    Bookmark   September 15, 2008 at 12:04PM
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I,m building a garage 20'x 30'It is a car detailing garage.So there is going to be heat and a lot of moisture.I was wondering if I should put a vapor barrier on the attic floor.And should I do my walls first over laping the plastic barrier from my inside walls to my attic.I don't know what to do first. Any suggestions.

    Bookmark   August 8, 2011 at 7:37PM
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Windows on Washington Ltd

The rooms over the garage are cold because the insulation that was installed into the joist bays has falling down and is no longer insulating the floor above.

As soon as insulation looses contact, it looses any effectiveness.

You can mitigate the issue by installing some blockers and spray foaming them shut or you can insulate that joist cavity by dense packing with cellulose or dropping the ceiling and spray foaming.

The same could be said for crawl space issues. The insulation has sagged and reduced the R-Value to a small fraction of what it was when installed (assuming proper installation).

Most issues with crawl space and garage spaces are a combination of air leakage and insulation misalignment.

You can go a long way to fixing the issue by just stopping the air movement.

    Bookmark   August 22, 2011 at 6:02PM
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