Looking for tips on why I'm getting condensation on the inside of upstairs windows. I turned the heat down to save energy only to find the bottom edge of the windows to have a lot of moisture. In some rooms I had the baseboard registers closed and got ice forming. This is with Pella double glazed windows. A friend's house with single pane windows and a similar heating setup has no condensation. I decided to open the registers and turn the heat up (was at 50 and now at 58) and this has largely solved it. But, I can see a noticable increase in oil consumption. Ideas?