It's not just me. I've found significant air leaks into my basement along the North and South walls; the West wall's leaking cold air on the ground floor, at the baseboards. I've filled the bigger gaps with backer rod (closed-cell foam) but caulking or other methods will have to wait. (can't foam it with the furnace running and the aroma of even low-VOC caulk's a bit much to sleep in. No wonder it's been so chilly at floor level!
You have to wonder -- was a serious coat of dust keeping the gaps plugged for the previous owner? It's not impossible, some of the worst leaks are where I replaced the floor of the room I use as an office and had vacuumed very carefully around the sills when we had the old floor out.
At least I found it. I was starting to think I'd gone poikothermic.
5 weeks ago