Foamboard under enclosed concrete porch floor
The back porch of my 1910 rowhouse in Washington DC was hastily converted about 10 years ago into a half bath. There seems to be little or no insulation for the half bath, which is getting quite cold despite being airtight with a newer window. Below the room is an open-air basement entrance way. A 4′ x’8 piece of 2″ rigid foamboard insulation would fit perfectly onto the bottom of the structure, which is concrete.
Given that the walls have little or no insulation, and can’t be accessed without ripping out the drywall, would insulating under the floor help at all, or just be wasted effort? Thanks for any advice.
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