What Is Pipe Insulation?

A tube of foam or fiberglass that fits around a water pipe, usually with a slit down one side so it snaps on. It slows the rate at which the water inside loses heat to cold air, and it keeps hot lines hot. It does not warm anything, so in a space that stays well below freezing for days it only delays a freeze. It works best on pipes in unheated areas that sit a little above freezing, like a basement, garage, or crawl space.

Self-sealing foam sleeves cost $5 to $15 per 6-foot piece and go on in minutes. Cover elbows and valves too, since they lose heat fastest, and seal air leaks where the pipe passes through a wall, since moving air steals heat faster than insulation can hold it.