I have a ranch townhome that was built in 1998. For several years now there have been loud "popping" and "cracking" noises coming from the attic. This seems to be heat related as I notice more in the hotter months in Colo. The noises, which are loud enough to wake me, sound like they are wood based, not metal. I've been up there and cannot see any irregularities. Would be interested to know if this is normal and if possibly adding a spinning attic vent would help. Thank you.