Crawl space wall insulation

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  #1  
Old 09-03-15, 09:30 AM
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Crawl space wall insulation

Hi All,

I hope I'm posting this question in the proper forum.

I'm going to place a vapor barrier, and insulate some, my crawl space. There is nothing but a dirt floor and concrete block walls. I was planning on putting 6-8 ml plastic on the floor, and styrofoam sheets on the wall, and blow some spray foam in the rim joist/floor joist spaces.

Is 8 mil plastic enough? (there floor's a bit rocky).

Would it be better to spray foam the whole wall, or will the styrofoam do?
 
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Old 09-03-15, 12:12 PM
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Welcome to the forums.

Your plan is consistent with sealing the crawlspace to the outside and opening it to the conditioned air of the home - is that the rest of the plan?
 
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Old 09-03-15, 12:54 PM
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I didn't really want it open to the rest of the house. My hope was to not have it separate from the house but vent it to the outside in the warmer weather.........I live in a region that gets cold winters.
 
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Old 09-03-15, 12:57 PM
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Then insulate the ceiling of the crawlspace instead of the walls.
 
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Old 09-03-15, 04:32 PM
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But i have plumbing down there. I thought i needed a little bit of house heat to passively leak into the basement?
 
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Old 09-03-15, 04:42 PM
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Just how cold is your climate?
Your plan is similar to mine here in Anchorage Alaska.
Here is a good information resource for my climate:

Welcome to the Cold Climate Housing Research Center | the Cold Climate Housing Research Center
 
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Old 09-03-15, 05:08 PM
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Let me start by saying I am a homeowner and not an expert - so listen to any of the pros before considering my comments.

When I bought my home five years ago, the floor joists of the crawlspace had fiberglass insulation; I added spray foam to the walls and a vapour barrier to the floor. I continue to vent my crawlspace in the warmer months and close it up in the cooler months. This system appears to work fine.

I have three thoughts that may help you to make a decision:

1. I wish I had a thicker vapour barrier. Trips into the crawlspace to upgrade electrical or plumbing, and to shut on or off the outside tap, have caused some small holes.

2. I wish I had spent more time upgrading electrical. Spray foaming really limits your ability to modernize your wiring.

3. Make sure your property is graded properly. I know that my vapour barrier keeps moisture from entering my crawlspace, but the work I've done to fix the outside grade really made a difference, too.
 
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Old 09-04-15, 12:20 PM
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In areas where freezing is a concern, it is generally better to seal the crawlspace from the outside and open it to the house air.
 
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