Air is a fair insulator, and one of the ways of insulating windows in a cold climate is to fasten clear plastic inside the windows, generally a couple of inches inside the pane. The problem is that moisture is frequently trapped between the window and the plastic sheet, leading to condensation on the window. Especially when the temperature outside reaches 40 below.

If you can get a tight enough seal that room air cannot get between the plastic and the window, there is a solution.

Ever heard of silica gel? You’ve probably run into it, in the form of the little packets used to keep things like pills dry. It’s also available in craft stores, for drying flowers. The kind I’ve gotten has tiny crystals in it that turn blue when dry and pink when moist. It soaks up moisture from the air when dry. When moist, it can be dried in the oven.

Have a small dish handy, of a size to fit comfortably on the windowsill between the plastic and the glass. Make sure the gel is thoroughly dry, and pour a few inches into the container. (I use small plastic glasses.)

The plastic I use has double-sided tape that is applied to the window frame, and I do the final drying while the tape is being applied. I then place the container of dried gel on the windowsill and apply the plastic, making sure I have an air-tight seal. The result? Windows that stay dry, even in the plant room.

Of course if the air is humid enough, condensation will still form on the plastic or the walls. But the window will stay a good deal drier with the gel than without it.