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cbzdel 03-13-2013 09:51 AM

Moldy Skylight
We have lived in out house for 3 years, nothing has changed building or weather wise.. We noticed that there was some drops of water on the floor under our skylight.. So upon closer inspection the wall surrounding the skylight is moldy about 1/2" around the frame of the window.

I called out of window company to quote replacing it, and they told me there is nothing wrong with it. He said its just condensation, and its due to the fact the skylight is in our kitchen above the stove/sink area so water moisture rises up into the skylight area.

He said there is not much I can do about this unless we find a way to control the moisture in the air and other than that its a poor placement for a skylight for reasons exactly like this on..

I have never heard of this before, any anyone put some truth to it? Also any ideas on how to fix the issue, If I am going to have a mold problem, I am just going to pull the skylight for good when I have the house re-roofed here in a couple months..

Windows on Wash 03-13-2013 09:56 AM

He is correct.

Stuff like cooking, washing dishes, opening the dishwasher, boiling pasta, etc will generate copious amounts of moisture.

If you can't do anything to control it (i.e. run a fan, open a door, etc), the moisture will go up and hit the cold surface and condense.

You could paint any wood surfaces with a mold resistant paint or put a small fan in that area to vent that space to outside the home.

Sorry to be the bearer of bad news in this case.

joecaption 03-13-2013 10:03 AM

Is there at least a vent over the stove?
Could always run a dehumidifyer.

cbzdel 03-13-2013 10:26 AM

unfortunately its not a vent to outside above the stove, its one of the recirculating vents, which I am not sure does much of anything. and due to its location there is not much that can be done to easily vent it to the outside.

I could possibly install a tiny vent up in the skylight area that is constantly running to vent that area to the outside?? maybe that would be the best and easiest??

Windows on Wash 03-13-2013 01:19 PM

Get a vent in conjunction with the roof install or get a venting skylight.

If you can get electricity up there for a powered fan, you should be fine.

Maintenance 6 03-13-2013 02:21 PM

It will help to make sure that the walls of the skylight shaft are properly insulated so that they stay above dew point.

cbzdel 03-13-2013 02:41 PM


Originally Posted by Maintenance 6 (Post 1136407)
It will help to make sure that the walls of the skylight shaft are properly insulated so that they stay above dew point.

We did that soon after we moved in, before that there were not insulated at all.

A venting skylight might be nice, it get SO hot up there in the summer I dont expect it is good for the walls and such.. I went up to clean the window on a 90* day and I came down soaked in sweat it must of been 120*+ up there haha..

Windows on Wash 03-13-2013 04:24 PM

Best time to do it is with the roof.

Get the solar powered ones and you get the tax credit.

Dave Sal 03-13-2013 04:35 PM

1 Attachment(s)
I had a similar problem as I have a skylight in my kitchen just in front of the sink and the stove. I insulated the skylight tunnel in the attic but plan to do a better job this spring and will use rigid foam insulation. The main thing that helped me is installing a grate above the opening at the ceiling and then installing a clear piece of plexiglass that sits on top of the grate which keeps the warm humid air in the kitchen from rising into the skylight tunnel.

cbzdel 03-13-2013 06:49 PM

that is interesting, did you seal it at all or just let everything sit there in the frame?

Dave Sal 03-13-2013 07:38 PM

It is not sealed but to do so would be a simple matter of gluing some self stick weather stripping along the edges of the plexiglass. The gap is probably less than 1/8" around the perimeter, small enough to keep the majority of warm air from rising into the skylight shaft.

asinsulation 03-14-2013 06:14 PM

I'd like to just clarify the skylight issue. Most of the time you will have fiberglass surrounding the enclosure in the attic, which is VERY difficult to install correctly, even for somebody who does it every day. Also, it is a major air leakage point and is rarely air sealed. Also, if the gasket around the window is damaged anywhere, or if there is no thermal break in the framing of the window, that will be an issue.

Best bet is to remove the insulation around the framing from the attic side and install either rigid foamboard or two part spray foam. If you do foamboard, be sure to airseal after to make sure it is effective. That will solve the issue in most cases.

If that doesn't work, you need to investigate the window itself. If the gasket on the double pane is not intact, it needs to be addressed. Also, if there is no thermal break in the window framing, there will be thermal bridging and high chance for condensation. At that point, replacement or additional venting is probably your only solutions.

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