Fixed 20 yr old skylight dome allows excessive hot or cold air to enter. Notice some of gasket between dome and frame has moved out of place. There are no water leaks during rain, but depending on weather conditions, the part of the aluminum frame inside the room "sweats" and moisture causes paint discoloration.

One installer would only replace the dome (actually an inner and outer dome), while another says he would replace the frame and the dome as a unit. He says it should have a new frame with a "thermal break" which is a polyurethane spacer which separates the inner from the outer part of the frame flange to reduce the heat transfer and eliminate the condensation forming.

I tend to think that if a new dome is installed with new gasket on the existing frame, the condensation should be eliminated. Also, I wonder about the integrity of the polyurethane spacer which is crimped between the two parts of the frame flange; whether over time the heating and cooling of the aluminum will cause leaks at the joints.

Opinions please and does anyone have long-term experience with the thermal break type of frame?

When it comes to skylights in general, I say replace as much as possible. If you only replace the dome now, and have an another issue in 2 years (which is common), then you'll be mad you didn't replace the whole thing.
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Roofing Contractors MetroWest, MA

Yes I agree. Replace everything. You may not have the right dome for the skylight or if you have the manufacture of that skylight the dimension may have changed a little. I have seen it to many times that someone wants a new dome and then it does not fit. replacing everything will eliminate future headaches.

If your replacing, don't go with a dome. A double insulated glass unit would be a better choice.
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selfemployedslave wrote:

If your replacing, don't go with a dome. A double insulated glass unit would be a better choice.

........provided it is "NOT" on a flat roof.

johne5
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johne5 wrote:

selfemployedslave wrote: If your replacing, don't go with a dome. A double insulated glass unit would be a better choice. ........provided it is "NOT" on a flat roof. johne5

Good point, I was assuming shingles
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johne5 wrote:

selfemployedslave wrote: If your replacing, don't go with a dome. A double insulated glass unit would be a better choice. ........provided it is "NOT" on a flat roof. johne5

Good point, I was assuming shingles
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Whatever your choice, just remember NOT to use glass cleaner or anything kind of solvent based cleaners as they tend to cause the dome to craze.
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Professional Roofing & Waterproofing Consultant