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Old 12-24-2008, 07:51 PM   #1
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Insulating my basement


I have a question on how to insulate my basement.

1. whats existing.... house was built 4 yrs ago. Unfinished basement ( This is what I am doing now). they put in by code for Omaha Nebraska 1 inch thermax foam insulation with foild on both sides. I framed the walls 2 X 4.
I have day windows on about 1/2 the house. Meaning that only 3 foot up of the foundation is covered with dirt.... A lot of the foundation is exposed.

2. I bought R-15 FACED insulation. I am at the point of insulation. I am using R-15 vice R-13 Cuz I want to max this out.

3. My question.... Will the Faced insulation be too much? since there is foil on the 1 inch foam thermax? I dont want to get mildew/mold.

Thanks Guys/Gals

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Old 12-24-2008, 09:37 PM   #2
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Insulating my basement


Yes, peal the face off of the insulation to avoid a double vapour barrier. The foam acts a moisture/vapour barrier and the face will double it.

When you drywall/paint be sure to use latex which will breath and allow the all to "dry" to the inside.

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Old 02-18-2009, 07:16 AM   #3
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If you are going to peel off a face, do it to the existing foam board.
Otherwise, I would put up my r-15 with the kraft face toward the living space, then put plastic sheeting over the studs before drywall.
You will want your vapor barrier to be pretty tight to avoid any condensation on the foam.
Don't peel the face on the new r-15 insulation, your vapor barrier needs to be at the living space, not in the middle of the wall. The humidity that the vapor barrier is stopping comes from the living space, the cold where it condenses comes from outside.
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Old 02-18-2009, 09:13 AM   #4
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Insulating my basement


You say this is 2x4 construction? Do they make R-15 in fiberglass batts that fit in the cavity of a 2x4 wall? Or are you going to let it expand outward a bit? I was under the impression that R-13 was the highest (in fiberglass batts) you could go to still fit inside the 3.5" cavity. Always thought that compressing insulation only negatively effected the R value.
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Old 02-18-2009, 02:24 PM   #5
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I've only heard of 11 and 13 too, but Owens-Corning marketing dept. might have figured out how to call it 15.
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Old 02-18-2009, 07:48 PM   #6
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Quote:
Originally Posted by cmbdiesel View Post
If you are going to peel off a face, do it to the existing foam board.
It's not the foil on the foam board that makes it a thermal/vapor barrier but the foam board itself. The foil was probably for fire code??

I too have read of the double vapor barrier issue and would not use the faced fiberglass batts.
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Old 02-18-2009, 09:04 PM   #7
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The foil is used to reflect radiant heat back into the living space as well as a fire retardant!
The ideal solution would be remove the thermax! Frame the walls, observing fire block requirements. Insulate between the studs, with unfaced insulation. Then fasten the thermax to the studs. Then, cover the thermax with drywall!
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Old 02-18-2009, 10:46 PM   #8
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Quote:
Originally Posted by Wildie View Post
The foil is used to reflect radiant heat back into the living space as well as a fire retardant!
The ideal solution would be remove the thermax! Frame the walls, observing fire block requirements. Insulate between the studs, with unfaced insulation. Then fasten the thermax to the studs. Then, cover the thermax with drywall!
As per the OP, it was done for code for an unfinished basement and doubtfully to reflect heat back into the living space. I would not remove the thermax. It was either bonded with an adhesive and/or fastened, it's already in place, paid for, sealed (or should be along all seems) and not to mention, the OP said he already framed the walls (hopefully at least 1" from the thermax). Take back the faced fiberglass or remove the facing and friction fit IMO.
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Old 02-18-2009, 11:04 PM   #9
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Yes its r-15 batts for 2x4's... I called owens corning. They said to put it normally then to breach the vapor barrier with a 2 inch slit from top to bottom every foot from top to bottom.
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Old 02-19-2009, 08:01 AM   #10
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Quote:
Originally Posted by luweee View Post
Yes its r-15 batts for 2x4's... I called owens corning. They said to put it normally then to breach the vapor barrier with a 2 inch slit from top to bottom every foot from top to bottom.
Excellent! Allows you to staple it in place and breach the vapor barrier.

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