Crawl space insulation question


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Old 04-15-09, 01:08 PM
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Crawl space insulation question

I am looking to insulate my crawl space after I had put down a 6 mil vapor barrier on the walls and floor. The recomended insulation is R19 unfaced that extends two feet onto the floor. That means I would have to use rolls instead of batts (otherwise I would be left with a bunch of 2 foot pieces).

Both HD and Lowes only sell the R19 unfaced in batts. Should I special order the unfaced roll or would it hurt to have the paper face against the existing 6 mil vapor barrier?

Thanks..
 
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Old 04-15-09, 02:17 PM
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Is your duct work down there?

Fiberglass insulation on your foundation is usually a tough way to go. Before you do any insulating with any material, you need to make sure you airseal your entire foundation. Otherwise you will never return your investment. I guess I need to know more...What has you set on fiberglass? Are you open to other options?? If it ever gets wet, it will wick up the fiberglass and it will fall down. I go into crawl spaces everyday and see fallen fiberglass a lot! If you are dead set on fiberglass....make sure you reinforce it by using a 1x2 or something to adhere it to the band joist.
 
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Old 04-21-09, 08:06 AM
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Fiberglass is indeed the worst choice for crawl spaces... or any below grade structure.

Crawl spaces are naturally damp and humid, and because the temperature inside it is always different from the outside, year round, any moisture in in tends to condensate over every surface.

The fiberglass soaks it, gets saturated, falls off. The resin used to hold it together is made with organic compounds so it also favors mold growth, even worse if it is paper faced. Paper faced fiberglass insulation in a crawl space is a mold farm waiting to happen.

According to the newest building science, and studies conducted by reputable independent organizations such as Advanced Energy and Habitat for Humanity, the proper way to treat a crawl space is to completely isolate it from the floor and outside air with a sturdy vapor barrier, deal it air tight, and then condition the space.
The encapsulated crawl space becomes part of the internal envelope of the house.

In the vast majority of the cases, you will not need any insulation at all after you encapsulate the space, because cold air will no longer be sucked into the upper floors through the crawl space.

An encapsulated crawl space make your whole house at least 18% more energy efficient, and way more than that if you have ducts running through it.

However if you will still want to insulate the space, go with rigid foam boards instead.

A couple of sites on crawl spaces:
http://www.crawlspaces.org (Advanced Energy)
http://www.dirt-crawl-space.com

You can also search Building Science Corp and US EERE (division of tge EPA) site for more info on proper crawl space treatment.
 
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Old 04-21-09, 04:36 PM
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Fiberglass would be the 2nd best choice. 1st choice would be closed cell spray foam. Fiberglass will not soak up moisture from the air so unless it gets wet you should have no issue.
 
 

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