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Garage door insulation

popea0128 | Posted in General Questions on

My garage is ice cold in the winter.  I can’t insulate the walls.  What kind of  product can I use for insulation on my garage door?

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  1. GBA Editor
    Martin Holladay | | #1

    1. Insulation won't help much if your garage lacks a heat source. Over the course of the winter season, the air temperature in your garage will stabilize at the average outdoor air temperature, regardless of the amount of insulation you install.

    2. Right now, your garage doors probably have a higher R-value than your uninsulated walls. The problem with garage doors is generally air leakage, not R-value (although the R-value of a garage door is usually low compared to a well-insulated wall).

    Once you get a heater installed in your garage, you may want to pay close attention to the weatherstripping at the perimeter of your garage door.

  2. popea0128 | | #2

    Thanks for your help.

  3. airfix | | #3

    With respect to garage door weather stripping my garage door company was telling me that brush seals are the best way to go. Does anybody have any suggestions for how to best weather seal a garage door?

  4. pakrat1 | | #4

    I used 1/2 by 2 wooden strips with flexible vinel strips to seal the sides and top of the door then ran thin foam weather seals between the panels both items are sold at HD or lowes
    after over 10 years they are still working

    1. jaccen | | #6


      Thanks for the picture. By chance do you have one a bit more zoomed out? I think I understand your concept, but a wider view would clear up my misconceptions.

  5. brad_rh | | #5

    Martin, I have to disagree with your statement that the garage will stabilize near the average outdoor temperature. My insulated, unheated garage stays closer to the ground temperature. I don't think it got colder than 50F last winter.

  6. GBA Editor
    Martin Holladay | | #7

    You're right -- estimating the average temperature inside a garage in winter is more complicated than I described.

    Whether or not your slab can help keep your garage warm depends on several factors, the two most important of which are your climate and whether or not there is any horizontal insulation under the slab.

    The colder the climate, and the more insulation you've installed under your slab, the more likely your garage temperature will approach the average outdoor air temperature.

    In a warmer climate, especially if your garage has no sub-slab insulation, the slab can help warm the air in the garage during the winter.

  7. davidsmartin | | #8

    Why is it recommended to put insulation under the slab of an unheated garage? If the garage is slightly below grade, wouldn't an uninsulated slab help keep the garage warmer if the walls are well insulated? Especially if the garage is attached to the house?

  8. Trevor_Lambert | | #9


    I didn't see him recommending insulation under the slab of an unheated garage, rather just stating some facts about what it would imply. An uninsulated garage floor is definitely preferable in an unconditioned garage at pretty much any time of year when the air temperature is above or below the desired temperature.
    *correction: it wouldn't be desirable in the following circumstance:
    ground temperature < outside air temperature < desired temperature
    In this case, the ground will be taking heat from the garage when you don't want it to.

    "Especially if the garage is attached to the house?"

    This part I think is wrong. At best, it's neutral. At worst, the heat coming from the house could be going into the ground. It would depend on a lot of factors such as ground temp, outside air temp, level of insulation and leakage between the house and garage.

    1. pakrat1 | | #10

      this is the trim / weather seal which I baught at home depot 10 years ago, hopefully they or someone still sells it. Also remember to put a thin strip of foam between the panels.

  9. jaccen | | #11


    Thanks for the extra pic. It's appreciated. Cheers.

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