Small Leaks Add Up, So Seal Them All

sually, the greatest number of leaks comes from small perforations in the ceiling: metal electrical boxes, drywall seams, and any place a wire or pipe comes through from below. Use expanding urethane foam to seal holes around PVC vent pipe (1), in electrical boxes (2), and especially at ceiling-corner drywall seams (3). If any of the sealing comes under local regulations for fire-stopping or draft-stopping, then use fire – or smoke-rated foam or caulking.