Another Crawl Space Insulation Question!

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  #1  
Old 01-13-15, 10:23 AM
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Another Crawl Space Insulation Question!

It must be getting cold out, seems like everyone is asking questions about how to insulate their crawl space.

Here is my situation/question.

Last summer I insulated my crawlspace by using pipe insulation on all the pipes and 2 inch rigid board attached to the walls, and spray to seal all the cracks.

However, the floors of my house still seem chilly and I am sure the crawl space is sucking out heat from the house.

I am thinking of doing one of the following:

1) adding another layer of rigid board to the crawl space walls
2) adding rigid board to the crawl space ceiling.. in other words between the floor joists.

Does anyone have suggestions on which would be more effective? Also, would I want to use 2 inch board again, or would a lesser width suffice?

Thanks for any suggestions, not looking forward to doing this project, but I think it needs to be done.

Side note, I do live in Michigan so it can get pretty cold.

Thanks for all your comments.
 
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Old 01-13-15, 10:26 AM
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Is the crawlspace open to the house air or the outside?

If to the house, you insulate the walls and not the ceiling. If to the outside, you insulate the ceiling and not the walls.

What's the floor of the crawlspace?
 
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Old 01-13-15, 10:36 AM
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The floor is dirt, with a vapor barrier in place.

To answer your question question about the air, the crawl space has two vented access points (which are closed during the winter), accessed from the outside. There is ductwork that goes through the crawlspace, but no actual heat vents heat the crawlspace.

Originally, I insulated the walls in order to make the crawl space more of a conditioned space to help keep the pipes from freezing.

Mitch17... are you suggesting that I should insulate the ceiling? Or did I misunderstand? Any thoughts on how thick of foam I should use?

Thanks again
 
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Old 01-13-15, 10:45 AM
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Yes, if you intend to keep this crawlspace open to the outside air and not the conditioned house air, then you should be insulating the ceiling of it rather than the walls - think of it as the floor of the room above is like an outside wall and should be insulated while the walls of the crawlspace require no insulation because the area is going to be roughly the same temperature it is outside.

That said, I prefer to make the crawlspace open to the conditioned air of the house and seal it off from the outside, in which case you have already insulated it correctly (not accounting for amount of insulation).

If you leave this as-is, I would put bats of fiberglass or Roxul (mineral wool - this would also be my preference) in the joist spaces leaving a couple inches of air space at the top. Then foil faced foam on the underside of the joists with the foil facing down and all gaps and joints taped with foil tape.

Hang tight for Bud to chime in as well, he's our expert in this area.
 
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Old 01-13-15, 11:25 AM
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Thanks for the info.

I am fine sealing off the crawlspace as that work would be much easier.
 
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Old 01-13-15, 05:14 PM
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Just a reminder if you plan to seal it off, you mentioned that you closed your crawl vents for the winter but you will want to seal them up with "cut to fit" 2 inch rigid board also. I learned the hard way that manually closing the vents does very little to keep draft out" and many winters they were leaking freezing cold air right under my family room.
 
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