Window Film Mullion Filler

The living room windows suffer from all the thermal problems you might expect in a late-1960s house, despite the slightly more recent storm panes, so I’ve been adding insulating film during the cold season. This works surprisingly well, although the tape holding the film tends to lose its grip in the angle between the (real, not pretend!) mullions and the window sill.

This year I added triangular fillers to ease the corner:

They’re Desk Signs from boxes.py, with the bottoms angled by 2.5° to compensate for the slightly misaligned sill and a small cutout clearing the paint accumulation in the corner:

A strip of tape down each side of the mullion and across the filler anchors the film, producing a slightly baggy fit. Next year I’ll use only one strip down the middle.