Is it okay to spray foam and gyproc a garage but not heat it?

4/25/2014 at 8:26:14 PM

No. Spray foam provides a vapour barrier preventing condensation and the growth of mold/mildew.

Mold and mildew occur when a surface is exposed to moisture. Generally, with pink batt insulation the problem that occurs is that warmer air from inside the garage makes its way through the batt insulation and meets with the cold roof deck (hot air meeting a cold substrate creates condensation), this works in reverse in hot climates.

Since closed cell Spray Foam is a vapour barrier at 2" the air within the garage will not be able to meet the exterior surface and will therefore not create condensation. If a garage is constructed properly with a watertight roof and a correct building envelope system then Spray Foam will prevent mold and mildew growth.

4/26/2014 at 7:35:08 PM

Just to add. You will not get any mold with pink or any batt type insulation if you have a properly fitted vapour barrier underneath the drywall. It doesn't matter whether it's heated or not.

If you have a heated room above the garage then I would recommend the spray foam. It's the best product and worth the extra expense to have a warm room over a garage.