[Marvin Gardens]

Polyurethane is the best for pipes. It should be closed cell to keep from absorbing moisture. Most of the time you only need to insulate the warm pipe unless you have freezing issues.

I have used the gray formed pipe (polyurethane) at the local hardware store for decades and it has worked fine for temperatures ranging from -30 to 160.

My solar hot water system is frying my insulation but it is at 212 on really sunny days and even though it is rated to 230 it is melting.

As for worrying how the stuff will do in a fire that is not really an issue. I mean, what are you doing in a house that is on fire anyhow????