Skylights with foam insulation over roof
So I am in the process of putting about 8 inches of foam on our roof. The house has skylights and with this we are Replacing the skylights with more energy efficient Fakro skylights. The skylights are located over cathedral ceiling made of 2x12s. Since 8 inches of foam will now be above the original sheathing along with 2×4 strapping to hold the foam/create a cold roof I am wondering what people have done in the past for placing skylights in this situation. The two options I have thought of are to box out the extra 9.5 inches with 2x4s this I think would create stronger support but will create more thermal bridging through the 2x4s. The other option would be attaching the skylight to 2×4 strapping which would have long screws attaching to the rafters/headers below. This option to me seems not as strong but would have better thermal performance. I am curious what others have done or typically do in this situation?
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