Insulating a basement ceiling


Old 11-21-08, 06:55 AM
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Insulating a basement ceiling

Here's my situation:

New house with an unfinished basement of which I have completed all of the framing and wiring. I plan on dropping the ceiling and installing recessed lighting.

What are the pro's/con's of insulating the basement ceiling between the joists with regular fiberglass insulation?...rigid insulation?

If using fiberglass, should I use faced or unfaced? Does it matter? Should the paper be facing the basement or the ceiling above?

Any ideas/comments/concerns would be greatly appreciated!

Thanx, all!
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Old 11-21-08, 07:31 AM
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This has been discussed ad nauseam on this forum. Do a quick search.
Old 11-21-08, 07:49 AM
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Basements are usually the least of your worries when it comes to insulation. In the wintertime, the coldest part of the basement wall is the part above ground, or near the frost line. So your primary consideration is framing and insulating the exterior walls, and rim joist.

The average ground temperature affecting basements (first 10') varies in areas where the ground freezes, but generally in the midwest the average is about 50F. So if you're attempting to keep your house 70F, that's a 20 degree differential. Insulating the basement ceiling will help, but the "bang for the buck" is greater elsewhere.

Many people insulate basements with fiberglass for the sound value. If the basement is unheated and kraft faced insulation is used, the facing would be up, toward the warm side. Many DIY'ers prefer to install the kraft paper down, since it's easier to staple up this way. But what they do not consider is the flammability of the kraft facing. If basement ceiling insulation is faced and will not be covered with drywall, it needs to be fire-retardant... something overlooked in many areas. So you'd actually need to purchase insulation that meets those standards (ASTM E84) which usually means it has a foil facing. If standard fiberglass is used, you could sheet the bottom of the floor joists with a fire-retardant paper or board which would serve the same purpose. Foil faced Thermax foam board also meets ASTM E84, and could also be used on the ceiling.
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