The last month or so, I would hear a big bang in my house. It sounded like it was coming from the outside. I thought something hit the house, so I investigated, but couldn't find anything. There was no snow on the roof to fall. It was quite cold though. It seems to happen a few times a day. Someone I work with said the same thing has been happening to them. Anybody have a clue what this is? Is it the wood expanding from the colder weather at night? All ideas welcome.