Looking for info on insulation dams between house attic and attached garage.

I can’t find any building standards for insulation dams between the house attic and attached garage. I inspected a new home recently and noted that some of the loose fiberglass insulation had fallen into the un-insulated garage attic. In my report I suggested installing an insulation dam between the house and garage to prevent this. The builder refuses to do it because it is not required. Any help would be appreciated.

Mike you simply made a recommendation and a insulation dam can be built easily by the new owner if they wish. I don’t see the builder doing this either and never seen a insulation dam between the attic and a fire rated sealed garage. The only place I’ve seen them is around the attic hatch.

I recently added about 24" of blown in cellulose in my attached garage attic. This has made about a 15-20 degree difference in the garage when the overhead door is closed. The garage is cooler in the summer and warmer during the winter. Most builders will not insulate the garage attic because it adds about $150-$200 to the cost of the home. I share my experience with clients who are interested in energy upgrades.

You made a recommendation. It is now up to others whether it is completed or not.

Linas beat me to it… screw the Dam… insulate the garage attic! Builders love choices!!! :wink:

I see insulation dams between the house and garage all the time. When there is 20 plus inches of loose fiberglass it falls into the garage attic which reduces the insulation value of the house in this area. I thought there had to be some kind of building/energy code that would cover this.

Yes it is an easy fix. I told the buy that this is an easy fix and explained what to do (he wants it corrected).

Thanks all


You could make the point that a vented attic over a garage, porch, or anything else would be no different than a soffit vent and would require some sort of an air barrier at the exposed edge of the insulation. Here lots of times it’s just cardboard.