We have a home in a cold location that is unoccupied during much of the cold season. (We're talking -30 F temperatures here.) It's well insulated and we keep it heated, but up in a far corner of the house, in a laundry room, the temperature can drop to about 10 deg less than the rest of the house (which we keep around 65).
The potential problem here is that the pipes for the washing machine run inside that exterior wall. Again, it's well insulated, but a 2x6" wall is only so thick, and I worry that pipe may freeze. The way we currently try to keep it warm isn't smart, IMO. There's an electric baseboard on that wall, and I set it to a spot where it keeps that room a minimum of 63-ish degrees. It kicks on for much of the winter, sucking a lot of juice, just in the hope that heating the drywall in front of those pipes will keep them above freezing when it's -30 or -40 outside.
I was pondering running a line from our boiler to a new register up there, when I realized maybe I could run hot water directly through the at-risk pipes themselves.
I wonder if running a hot-water recirculator designed for systems with no return line (as we have none) wouldn't be a smarter and more energy efficient solution. Something like this one: https://youtu.be/Jd0IsylW4Cc
There's a utility sink up there which would be a perfect spot to stick a bypass, and it's the furthest line in the house (and bonus, it's behind the shower we use, so it would save us on water not having to wait for that to heat up.) It's probably a run of 30 feet. If I understand things correctly, that would run the warm/hot water through both the hot/cold lines as programmable intervals. I figure a couple of times per hour would do the trick, and we have a pretty efficient (and low cost) water heater with a huge tank.
This would save me a ton of worry, and it would also let us heat the home to a lower temp (50s) without worrying about that one pipe run. (All the other pipes are inside walls or under the heated slab.) I imagine I could get system and my plumber to install for about $500, and between the excess fuel burned keeping the home extra warm just for this pipe, and running the baseboard as a backup, this would probably pay for itself in overall energy savings in a year or two.
Edit: FWIW, prior owner lived there for 2 decades without freezing up this pipe, but I don't know where they ran their temps and the baseboard all winter. (Pipe they ran into an unheated attached garage did burst -- that I have seen -- and it was disclosed during sale. I removed that line -- was to an unnecessary hose bib -- and capped the line in the interior wall.)