Insulate or Heat Tape? What Foam Sleeves Actually Prevent
One step of protection, measured
Foam pipe insulation does not heat a pipe; it slows the rate the water loses heat. In practice it moves a pipe in unheated space from freezing near 20°F to near 10°F. The question is what that buys where you live. Of 2,938 counties that get at least one night below 20°F a year, insulating removes a median 73% of the nights a pipe is at risk.
Three kinds of county
| After insulating | Counties | What it means |
|---|---|---|
| Under 1 night below 10°F | 623 | Foam is the whole fix |
| 1 to 9 nights | 830 | Foam plus the night-of routine on those nights |
| 10 or more nights | 1,485 | Foam is not enough on its own |
The coldest end: Southeast Fairbanks Census Area, AK with 162 nights below 10°F, Yukon-Koyukuk Census Area, AK with 152 nights below 10°F, Copper River Census Area, AK with 144 nights below 10°F.
When heat tape earns its place
Heat tape (a thermostatically controlled heating cable taped along the pipe, under the insulation) is for runs that still face many nights below 10°F, and for runs you cannot insulate well - a supply line to a mobile home, a pipe crossing a vented crawlspace. A 12 ft kit runs $17 to $37; an average burst-pipe repair is about $500, before water damage. In a county like Ringgold County, IA, with 33 nights a year below 10°F even for an insulated pipe, it is the cheaper side of that trade.
Use it safely
Use a cable with a built-in thermostat and a UL or ETL listing, plug it into a GFCI outlet, never overlap it on itself unless the maker says that is allowed, and check it each autumn. Old or damaged heat tape is a known fire cause. If a run is long, inaccessible or keeps freezing, the better fix is moving the pipe or sealing the space it runs through.
Where to go next
See the range: Hennepin County, MN, Cook County, IL, Harris County, TX, Miami-Dade County, FL.
When Freeze Season Starts and Ends, by Latitude · How the County Freeze Numbers Are Made