My trip home for Christmas gave me my first shot at using my thermal IR camera in quasi-freezing conditions — it ended up being warmer than usual, but still dropped to freezing, or close to it, when the sun was down. I did a survey of my mom’s and a neighbor’s house (confirming for the neighbor that the section of roof where the snow melts fastest is warmer than the rest). Not surprisingly, the warmest parts were the windows, and we have lots of windows. The largest ones are now double- or triple-pane, so it used to be be worse.

Several basement windows, though, are still single-pane. The whole idea of insulation is to trap dead air, i.e. it won’t convect and it also conducts poorly, so I tried a little experiment: putting some bubble wrap up against the window, wrapped in some thin packing foam. I left a slice of it uncovered as a control.

You can see that the left side is noticeably warmer than the insulated part. I went online to see if anyone made insulation made specifically for glass, and ran across a site that had done pretty much what I did — just using two layers of large-bubble packing material so I went out and bought some. The basement windows are now no warmer than the rest of the cinder-block walls. The bubble wrap is translucent, so most of light still gets through.

I used the last of the wrap on some windows on the north side of the house, so I’m not blocking any incoming light that helps heat during the daytime. In my test, I blocked off one section

The window I tested is the one on the left. It’s slightly cooler than the rest. I used one of the other FLIR programs to confirm it’s about 1 ºF cooler than its neighbors (those pictures don’t get saved to the camera roll, though. Not sure why). These are multi-pane windows so the effect isn’t as dramatic, but every little bit helps, so I ended up covering up a few more windows to use up the bubble wrap I had bought. They’re in a part of the room that’s partly blocked anyway, so it doesn’t really impede looking out. This could be re-used from year to year (the basement windows probably left up permanently) and only took a few minutes to do.