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Crawlspace insulation question


DKG's Avatar
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Join Date: Apr 2002
Posts: 26

03-10-03, 02:11 PM   #1  
Crawlspace insulation question

I was in my crawlspace today and have a question or two about it. Looking up I see a layer of foil sheathing attached to the bottom of the joists. Sandwiched between the floor above and the sheathing is batt insulation. Rodents have chewed through the sheathing and I think are nesting in the insulation between the sheathing and the floor above. I'm thinking I want to remove the sheathing altogether so there isn't this space for critters to run around in. I seem to recall my home inspector told me I should remove the sheathing anyway. If I removed the sheathing I guess I would need to staple or otherwise fasten the insulation to the joists. Then the batt insulation would be directly exposed to the unheated air.

Was my inspector correct that I shouldn't have foil backed sheathing as the bottom layer of a crawlspace. If so, should I just leave the insulation there or should I repace the sheathing with plywood?

Thanks

 
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resercon's Avatar
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NJ

03-10-03, 08:38 PM   #2  
Insulation was installed backwards.

http://www.eere.energy.gov/consumeri...riefs/bd4.html This is an U.S. Dept. of Energy brief on Vapor Diffuser Retarders (VDR) or what is commonly known as vapor barriers. The vapor barrier should touch or be against the warm side of the home. Meaning to say having the foil sheathing under the insulation in a crawl space is wrong. The correct installation is when the vapor is on top of the insulation in a crawl space.

The easiest way to install insulation in crawl spaces is by using joist hangers. They resemble metal coat hangers with sharp ends. They are a little bit longer than the width between your ceiling joists. The way the insulation is installed is it is put up first with the vapor barrier facing upwards. A joist hanger is then pushed under the insulation every 3 to 4 feet and the sharp ends of the joist hangers dig into the joist and hold the insulation up.

This will not get rid of your little critters. The only way you are going to get rid of them is by calling an exterminator. You could set traps yourself.

 
DKG's Avatar
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03-11-03, 07:28 AM   #3  
Thanks - and a follow up question

Thanks for your response. One follow up question - I think the yellow fiberglass insulation is unfaced on both sides. If so, can I just switch the order of the sheathing and insulation (i.e. shove the foil sheathing all the way up against the floor, then attach the unfaced insulation underneath using the metal hangers as you describe? Or do I need to remove both, and replace with new, faced insulation?

Thanks
DKG

 
resercon's Avatar
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NJ

03-11-03, 09:01 AM   #4  
You can shove the foil sheathing up against the sub-floor and then install the unfaced insulation and you do not have to purchase more insulation. I would like to caution you about the little critters, be careful and mindful when removing the sheathing and insulation. Wear protective gear when doing so too. Some of the insulation you may not want to re-install because of nests and other things. Do what you can then measure the amount that you need and then go out and buy the insulation. Good luck with your project.

 
DKG's Avatar
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03-11-03, 09:10 AM   #5  
Thanks again

Thanks again. I'm glad I can reuse the insulation, although some of has been shredded by the critters and will have to be replaced. Thanks for the warning also - I just know I'm going to find awful things up in there. Ugh. Home ownership.

 
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