No insulation over attached garage???

Came across this today…The homes insulation was in good shape but there was no insulation over the attached garage. Would you call this out?

No, it is quite common.

I find it all the time. I tell homeowners its a Saturday afternoon for you and a buddy, or hire a pro if you don’t know what you are doing.

No, I mention that there is none, but it is not a defect.

I don’t know how things are done your way, but if you travel 145 miles north east on 44 you’ll never see it. No, I wouldn’t call it out or even mention it unless the listing states an “insulated” garage.

If it is a heated garage it will contribute to a significant energy loss and I would call it out. If the garage is a cold room then I would describe the lack of insulation as typical.

Insulation is required for conditioned areas. I see it like this 99% of the time. Unworthy of mention.

Never have seen insulation over any garage, attached or unattached. Now if it was converted to a room, different story, but then it’s not a garage anymore either.

Heat rises (stack effect) if there is nothing to resist it then it will be an energy loss and could even be conducive to mold/mildew under the right circumstances, lack of ventilation etc.

About 50/50 here

The garage is unventilated. What’s the point spending money to keep the “heat” from rising. And what harm will it do to rise into the attic where it can mix with its own kind?

Please be more specific about an uninsulated garage can contribute to “mold/mildew” under *any *circumstances.

I had a client call last winter and complain about frost forming in a bedroom closet above the garage. The garage and closet were insulated but the air barrier was not sealed at the bottom of the closet floor. This allowed cold air to migrate and when it met the warm interior surface it condensed and formed frost. Indoor humidity was 75% which was another factor.

Meyerott Inspection 023 [640x480].jpg

Meyerott Inspection 024 [640x480].jpg

Meyerott Inspection 020 [640x480] Baseboard.jpg

When the heat rises it will pass into the attic. If uninsulated and lack of ventilation the heat will rise to the bottom of the roof sheathing and cool down due to exterior temperatures at night and in the winter.

Cold air cannot retain as much moisture as warm air can. Therefore, when the warm air cools off on the cold sheathing it will shed moisture.

Insulation and ventilation work hand in hand and will perform to different levels depending on the variables involved.

I have seen some attics perform well with lack of ventilation and others with significant mold/mildew issues (moisture over 19%).

A good rule of thumb is 1 square foot of roof ventilation for every 600 sq ft of attic floor space.

We ventilate to remove moisture content in the air. We insulate to retain the heat although it will eventually pass through.

Here is a link regarding insulation and ventilation from Carson Dunlop :

We don’t have much problem with attic condensation down here, at least I’ve never seen it. If I were to recommend garage insulation in this part of the world, I’d be laughed out of the profession.

You provided a link to a 30 page document. Sorry, but I don’t have time to read that.

Again, we’re talking about an unventilated garage. It would seem to me that the air in the garage would be cool, if not cold, in the winter when condensation issues may be present. Have you actually seen issues with condensation because garages were uninsulated?

If it is an unheated garage then lack of insulation is a non issue.

Ventilation of cold rooms is a good idea.

Performance may vary under different conditions regarding volume of insulation and ventilation.

Do I see condensation issues above garages?

I see condensation issues anytime cold and warm air contact each other when there is lack of ventilation. Sometimes above garages, sometimes in insulated attics sometimes in crawl spaces.


Heated or not, it’s not considered a “living” or “habitable” space (according to the UBC) and therefore, does not require insulation in the attic or walls.

I have heard the wise ones speak of cold air, and warm mosit air, I just thought it was a myth.

Not many insulated garages here either. I had a HI come behind me and call out lack of insulation over the covered Patio that was in an area under the roof. Now why would you insulate a patio cover???