Need advice on closing in porch
My house is in the SE Texas Panhandle, in zone 3B, but only 15 miles from Oklahoma (zone 3A) and also only 15 miles from the majority of the panhandle (zone 4B). So we have a very mixed climate that in my lifetime I have seen range from -15 degrees to +115 degrees F. Some years it is quite dry and some years quite rainy and humid.
A few years ago we built a lean-to covered porch along the full north side of our house, approx. 10’x32’. We poured a 4” concrete slab with 8”x8” footings, but no insulation, vapor barrier or anything else underneath. The porch roof is white steel, over plywood decking, completely unfinished underneath. Due to an overhang over one small portion of the porch, there was room for only 2×4 “rafters” under the decking, not 2x6s, which we would have preferred.
Now I would like to enclose the porch, dividing it into 2 rooms, a guest bedroom and a mud room (and also to serve as a buffer for the main part of the house from the north wind), but I have questions about how to best insulate the area, given my restrictions.
The mudroom portion of the porch I am okay with just leaving bare concrete (although I may decide on covering it with porcelain tile). I was thinking about putting a good pad and carpet in the guest bedroom, as the only way I could think of to help warm the floor up a bit, but I didn’t know if I was just asking for mold to build up under the carpet. Should I go with some good porcelain tile and throw rugs, instead?
Since I have only 4” of insulation space in the ceiling, what will give me the best bang for my buck? One thought that I had was that after insulating, instead of (or perhaps in addition to) using sheetrock was to install metal ceiling tiles, the shiniest that I could find, to possibly work as a radiant barrier … would something like this reflect the heat back down into the room, rather than allow it to leave through the roof? Would I need to seal all the seams between the tiles to keep heat from escaping, and if so, what is the best product to use?
To minimize thermal bridging, there will be no openings in the ceiling/roof or outside walls at all (for light fixtures, fans, electrical outlets, light switches etc.), and I plan to buy the best insulated exterior door I can find. There will be only one small triple-pane window in each room.
I would appreciate any and all advice/ideas.
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