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JimNW 01-14-2010 02:12 AM

condensation on skylights
new forum member here. My question is regarding some condensation on my skylights. First, let me explain that the skylights are located in an awning on the exterior of the house. We added on this new awning and skylights to match an existing awning and skylights leading out over our deck. Since it is all open (haven't finished the underside- just framed out for now) I figure that the temperature on both sides of the skylight are relatively close and cant understand why the condensation. It is a flat glass skylight (not a dome). I live in the Pacific NW and as you may have heard, lots of wet weather up here. Now, I haven't installed the weather stripping yet but can't imagine that it would be the deciding factor. I appreciate any advice you may have for me.

Bob Mariani 01-14-2010 07:17 AM

Heat rises and is trapped along the joists near the skylight. The glass is colder than this warm air. When moist air hits a colder surface it will condense.

JimNW 01-14-2010 04:22 PM

Bob, thank you for the reply. I understand the process of condensation, I guess I'm curious as to why the existing skylights don't "sweat" and these new ones do. And how I can combat the condensation. The only difference that I can see, is that the existing skylights have a finished awning. Maybe they are also insulated in that space but I can't see why they would have insulation there. Its on the outside of the home and not over any living space. Would a diagram or pictures be helpful or am I making a mountain out of a mole hill?

Bob Mariani 01-15-2010 07:02 AM

It could be the new ones are not leaking the moist air to the exterior as the old ones are.

Tom Struble 01-15-2010 08:27 PM

could just be moisture in the new framing material

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