As I may have mentioned, we pulled down all the trim in our house, including around the windows. Aaron has noticed some slight air leaks and wanted to fill them in with "Great Stuff" foam to make things more air tight. I was under the impression that you wouldn't actually want things to be "air tight" in a house (similar to when that stupid idea of duct taping your house shut came about). He filled in spots where you could actually feel a breeze/draft but I was hesitant to let him fill in everywhere and end up with not enough air getting in the house.
Does anyone know the guidelines on this? I assume there is a minor about of air getting in via the window sills/sashes, although they are thermal pane.