I have a problem with condensation build up on the inside of my windows on the main floor, I am told this is a result of being built air-tight. I have a gas fire place in the basement that heats the house. I do have electric baseboards on both levels but are never turned on. My problem is that the condensation builds up, freezes, and then when the sun hits the windows it melts into the window frames and eventually will start to rot. My question is what can I do about this. Any suggestions would be mostly appreciated!!