Thanks for your reply on heating cables for plumbing. I should have also asked how is the best way to insulate them? The pipes run side by side between the joists for about 24 ft. They come down below the joists in the 10 or so feet.
Answer:
There are all kinds of insulating packages on the market but the best I've seen remains wrapping them with bats of R-20 glass fibre and running a strip of tape around the whole thing every foot or so.
