That and there was no wind last night. My house was built in the late 70's, so there's no Tyvek wrap. Even though I've replaced windows and doors as well as sealing and insulating the attic, wind can seap in through the walls. Plus, I have a chimney for the oil heat and that makes air infiltration easier by creating an exit. Not that fresh air in the house is a bad thing, but it does allow the house to cool quicker on windy days/nights than on calm.