Beginning in the fall our 4 year old home develops sweat on most of the windows every day. It seems worse when there is heavy frost outside. I understand that it is due to a tight home, but with an air exchanger already installed and keeping windows cracked, there still is no noticable difference. We have been running the furnace fan constantly which seemed to make a slight difference. Everyday, I try to wipe up the moisture at the bottom of each pane, but it is neverending. I dread replacing the windows due to wood rot in a few years with this ongoing problem. Any suggestions?