Garage insulation


Old 01-13-10, 11:13 AM
Thread Starter
Join Date: Apr 2009
Location: NEPA
Posts: 20
Garage insulation

My garage, in PA, no living space over it, has old fiberglass insulation at the floor joists, but no celling, would like to take it down and put ridige insulation between the rafters at the roof, want to leave it open, no celling, will this work, to keep it warm, do I need a vapor barrier, have a forced hot air burner in the garage, burner was in the house but was to small.
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Old 01-13-10, 11:40 AM
Join Date: Oct 2008
Location: New England
Posts: 9,995
Hi Steve, I think I've got it. Currently fiberglass in your garage ceiling and you want to remove it and use rigid insulation, cut and fit between the rafters.

If you keep the garage heated, the vapor barrier would go on the warm side. The rigid insulation can be the vb or part of it, but up next to the attic floor, you would not be able to add more insulation, if needed, like fiberglass. As the vb would be in the wrong location. However, you could add more rigid insulation and simply go thicker, since air does not flow through the foam.

The rigid would need to be a tight fit, or sealed with can foam, but yes it would help to keep the garage warm.

BUT, I didn't see any mention of other insulation, like walls, unless I'm lost from the description.

The other question would be, how much insulation. At R=5 per inch or so, it takes two or more inches to get the heat loss down anywhere reasonable, and 8 inches to meet recommendations. That's expensive.

So what is on the walls and was my take on your description correct?

Old 01-13-10, 02:40 PM
Thread Starter
Join Date: Apr 2009
Location: NEPA
Posts: 20
Was going to put some kind of insulation on the block walls, and on the 10 foot garage door, heat only stays in for about 10 to 15 min now, kind of hard to work on my Hot Rod like this. Thanks for the info.
Old 01-13-10, 02:50 PM
airman.1994's Avatar
Join Date: Dec 2005
Location: VA
Posts: 5,632
Fire code will call for foam to be covered.

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