a kid visits and opens the upstairs windows. Had a get together yesterday - a young boy was too hot upstairs and opened two windows (wide open) and never closed them. We didn't use the upstairs last night, so never noticed. Had a big fire last night and woke up to a pretty cold house - unheard of. Had a big fire this morning - came home to a chilly house at noon. Just felt a rush of cool air coming from the stairs and could smell fresh air - sure enough, about 30 hours of wide open windows. Just had to laugh. Cheers!