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Insulating a lean to porch

My house was built in 1982 with a lean to porch. I enclosed the porch and now need to insulate the roof on the porch. The ceiling consists of 2 x 6 rafters with open perlin and a metal roof on top. I need to insulate between the rafters but the ceiling is already low and I can't drop it down enough to provide a proper vent space above the insulation.

My thought was to remove the metal roof, add decking and tar paper then 2 x 4 perlins on top of tar paper and then a metal roof. I would then add 6" of insulation between the rafters. Would this give me enough air gap between the roof and insulation? Since this is a lean to porch, there is no way to let air out at the peak of the roof. I live in central Texas and the temp. gets over 100 degrees in the summer. Any advice would be greatly appreciated.


Timothy Miller
Re: Insulating a lean to porch

Howdy, how about installing fiber glass insullation in the joist cavity then 4 by8' by 1" insullation foam panels as the ceiling or then drywall over the foam. Your perlins above the joistsallows air flow as long as you do not insulate above the joists.

Re: Insulating a lean to porch

Thanks for the info. I was just worried about enough air space above the insulation.

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