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Discussion Starter · #1 ·
My basement is 2,400 SQ-FT and in the construction I put DOW Thermax board insulation on the basement walls. The basement is a zone on our HVAC Air system. The house is fairly well insulated but I'd like to do a bit more. The sill plate does have foam but it's also a poured foundation and there seems to be some gaps.

The problem is that the DOW board was put up and the sill plate was not completely sealed. The second problem is that I have felt air infiltration in the joist bays above the sill plate. In the one picture you can see that I took out the fiberglass and used a foam gun to seal it and the sill plate. Problem is the gun does not work very well, especially since the bottles sit on top of the gun. I tried a caulk gun and that was easier but it doesn't offer as good a seal or insulating value as the expanding foam.

I thought about cutting foam blocks and sealing them into the cavity. But, what would I use to seal them in place? Again, the insulation gun does not work well in tight areas.

I thought about using a spray foam kit. Not sure how well this will work but I don't think with the house being lived in that it should be used in such a large scale in living space. All the living space is conditioned and goes through one air handler.

I don't think the fiberglass is worth using although for some reason I could not understand the inspector wanted it.

Thanks for the help...

John
 

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Cheapest way, especially if you are not counting your labor, is to use netting, housewrap, or reinforced poly to go from the bottom plate to the subfloor, and to both joists. then dense pack cello, behind that.

My preferred way to do it is to use 2" High R (foil faced) rigid foam and foam it in place either with a foam gun, or with the cheap high expansion foam from the hardware store. This method is a bit more expensive, but in my opinion far better.

You can also use 2 part foam. I see no reason why once it's applied and cured (2 mins +/-) it wouldn't be safe in your home. If you are really concerned paint it.
 

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I thought about cutting foam blocks and sealing them into the cavity. But, what would I use to seal them in place? Again, the insulation gun does not work well in tight areas.


John
To get into tight places, buy some clear tubing at the hardware store and attach a length of it to the end of the spray can. You can now keep the can out of the bay and get the "hose" up in there.

Ditto what Zab said. Cut foam blocks to fit up against the band and "glue" it in place with the foam.

Double ditto - Closed cell foam is not the same as the old formaldehyde.

Hope this helps:thumbsup:
 

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Discussion Starter · #6 ·
I have done some experimenting with the dow-board and using the foam gun and tubing. The tubing slows the foam and clogs. It works but not well and wastes lots of foam. I am going to wait until spring and then remove the fiberglass and fiddle around with it. In one area on the west side of the house where the outside of the house is rock I actually have ice behind the pink insulation against the sill band. Since the house was built we've had high moisture levels in the basement and part of the reason is it's a poured foundation. After I pull the pink out and the moisture level of the basement is low I'll probably foam in place the dow-board.

To the point of safety with foam. Maybe it was something I heard or read but we're not completely convinced spray foam is safe. For this reason I can't use a lot of it but it's okay if I use the small cans for sealing. The problem seems to be in the off-gassing which you might say stops after the foam cures. Are you sure of this because not everyone is. I think a decade from now we'll have the answer but for now we don't know for sure. Don't bother to debate me on this because I won't and so you win right off the bat. As for foam board, it has been found to be safe and has no off-gassing.
 
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