Foam insulation

I'm sure all my readers know this... but why not say it again? Once your windows are in, but before putting on the extension jambs, be sure to insulate the area between the window and the wall (see bulging beige stuff above). Although it means going window to window and trimming it back to the casing with a utility knife after you foam it in, it will pay off with years of cozy warmth in winter. This goes for doors, too.