I have flying squirrels getting into my attic, and I'm trying to seal all possible points of entry. Today I was up on the roof and noticed that the vent on the side of the chimney has been breached by some critter, and based on the damage and the size of the vent, it seems likely that this is the (or maybe one) entrance for the flying squirrels. I don't know how they would get from inside the brick chimney to inside of the attic, but it's possible that there's a crack somewhere in the chimney that opens up to the attic that I can't see. We don't use the fire place due to asthma. The vent is installed directly into the side of the brick chimney. It's possible that it could be replaced, but I can't find an exact size match, and given that we don't use it I'd rather just plug it with foam or whatever.
