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AaronFrank
Adding Insulation to attic
AaronFrank

We recently purchased a 1960's Levitt home that has 6" of paper faced attic insulation. Part of the attic has osb so the space can be used for storage.

The attic leaks the second floor warmth terribly. A couple of questions about adding additional insulation:

1: Is it absolutely necessary to pull up the OSB, or can the R-30 or R-38 rolled insulation be pull right over it?

2: Can I use paper faced insulation again? Or, does it have to be unfaced?

3: The paper faced R-38 is, strangely enough, cheaper than the unfaced R-30. If it is necessary to have the unfaced type, can I just peel the paper off?

(I recognize some of this might have been answered before, but didn't see this specific set of questions.)

Thanks.

keith3267
Re: Adding Insulation to attic
keith3267

You can lay it over the OSB. You should use unfaced but you can use faced as long as you don't seal the faces to each other.

HoustonRemodeler
Re: Adding Insulation to attic
HoustonRemodeler

If you have eave ventilation, the insulation should not touch the roof decking. Use these to allow the eaves to breathe to the attic space.

Remember you are trying to stop the air flow (chimney effect) from the inside of the house to the outside, not the outside through the attic.

Fencepost
Re: Adding Insulation to attic
Fencepost

The above is good advice.

The "paper" (properly called "kraft facing") is a vapor barrier containing an asphalt product that prevents moisture transfer from the conditioned space into the insulation. If water vapor were allowed to enter the insulation, it would condense on the "cold" side of the insulation, drip back through the insulation, eventually saturating all of the insulation and reducing its effectiveness and potentially causing water and rot damage to the structural members of the house.

If you add kraft-faced insulation, the facing should be down. Unfaced is a little better; if some water vapor did get past the original vapor barrier, it could be trapped in the old insulation by the vapor barrier of the new insulation. However, the vapor should be minimal so it may not be a problem. If the existing insulation fills the joist bays (the top of the insulation is at the same level or above the top of the joists), then run the new insulation perpendicular to the old stuff. This will cover the joists and reduce heat transmission through the framing.

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