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old scrambled
unheated garage insulation

I wish to insulate an unheated garage, primarily to limit summer heat, in the Sacramento, CA area. I'd like to put fiberglass batts between the roof rafters and wall studs and drywall over the bottom eight feet on the walls, leaving the inside of the gables and rafters uncovered. I know the vapor barrier goes toward the warm side in winter but in this area we get some sunny days. So some days the roof and walls are warmer outside than inside and on other days it's opposite. My question, if anyone knows, is which way does the vapor barrier face or do I even need to be concerned about it. It's generally quite dry here but can get very foggy in the winter.
Thanks for your help.

Timothy Miller
Re: unheated garage insulation

Howdy, i would install drywall on the ceiling and then install insulation on top of it say R38 for over kill .. R22 would likely be enough. Why? So the roof can be vented above it which will keep it cooler in the summer and no vapor barrier would be necessary in the ceiling framing.

Re: unheated garage insulation

Considering this is an unheated garage and if there are no plans to turn this into living space there's no need to consider any vapour barrier.

Also, you might also consider insulating the gable ends.

Re: unheated garage insulation

Why insulate a non-airconditioned garage? It's going to be a lot hotter for a longer period of time. Essentially you're going to keep the heat inside. Are the other two walls and garade door insulated?

Spend the money ensuring your attic is well ventilated.

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