I have a raised bungalow with a 20″ overhang. In the winter months the floor over the overhang is freezing(full, heated basement). There is currently fiberglass insulation packed into the joist cavities. I am wondering about removing the fiberglass and spraying urethane foam into the cavities. First question is this a wise move and if so on which surfaces would I apply (or have applied) the foam.ie. bottom of subfloor, sides of joists ? Where is the air space required to be effective. I have talked to several insulating professionals and I am getting totally different answers to the same questions.
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First the foam will improve greatly your comfort level at the overhang.
Overhangs are always a pain in the ass area that requires special attention to include it into the controlled space of the main house.
The trouble with most of them is that they are typically cantilevered past the foundation with a double end joists. Most designs also require blocking between the basement space and the outside space. This prevents any of the heated air from reaching this dead cold space.
Unless you can circulate warm air underneath your feet, you will have cold floors. You can add radiant heat but this could be costly for this outside strip.
If you have blocking that prevents your basement heated air from entering this area, knock em out and replace with 2x4s on the flat.
Spray the foam on the bottom and ends, leaving the top or underside of your floor exposed to the basement heat.
Wish I could be of more help but it's a bad design for conventional heating practices. It exposes a critical area to cold.
Gabe
Thanks for the input. I was thinking along those lines as well, the joist cavities have no blocking so air will circulate. I will probably buy a foam gun and a couple cases of high expansion foam if the costs aren't to prohibitive. A local insulating company that subs to the GC I work for said he'd do it for about $400.
Thanks again!