| Do you have aluminum frame windows?  Will the replacement be a retrofit?
 How is the insulation in the attic? Is is compressed?  I added an extra layer of R-30 and it made a big difference in equalizing the upper and lower level temps.  Attic insulation is relatively cheap if you do it your self (but hot and dirty).  I think the attic insulation made more of a difference than the dual pane windows.
 |