We need to spend more time in the basement.
Our house is shaped like a capital I. One half of our basement is storage. We have giant rolling metal shelving storage all around the outside walls and the floor is concrete so it's great for bringing in the animals when it's super cold but we don't generally spend much time down there.
Extreme wind hit today and my husband noticed an appreciable drop in temperature in the indentation that is the middle of the I. So he poked around behind the shelving units and found a snow drift inside the basement. He poked around a bit more and discovered that the entire lower sill on the window behind the unit had both rotted and been chewed through. So the wind blew the snow through the opening which was about three inches. He fashioned a new one out of wood we had lying around and blocked the opening but then we shoveled out the snow and there was about six inches of leaves underneath that. Clearly this has been going on for months.
Unbelievable. We need to spend more time in the basement.