Condensation on Skylight After Insulating...Is This OK

chipster_2007November 6, 2011

I just insulated the skylight that is in my cold attic with 1 1/2" of a foam square, foiled on both sides. I thought I had a good tight fit until I took down the foam block today and noticed some condensation on the lower part of the skylight , about 10% of surface area of the glass). It had onlly been up there for 24 hrs. Is this to be expected or is there something else I need to do to resolve this? Thanks

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Warm air from the attic is hitting the cold skylight. The tighter the attic -to-house interface is and the more insulation, the less likelihood there is for condensation to appear.

    Bookmark   November 6, 2011 at 3:37PM
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So, you are just trying to insulate the skylight for winter?

Why? The attic is in the cold zone, right? If you want additional insulation, it needs to go between the cold zone and the warm zone - eg the attic floor. It really doesn't help to try to insulate a cold attic from the cold outdoors.

    Bookmark   November 7, 2011 at 9:19AM
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