wrote in message oups.com...
I have been helping my aunt excavate her back yard, in order to expose
hot water pipes, that run about 30 feet from the house to the garage.
Both the hot water heater and the natural gas boiler are in the garage.
The pipes are not insulated and are just about 18 inches below grade,
in Cambridge, Maryland (8 feet above sea level). Last year's heating
bills were astronomical, and my Aunt thinks that a lot of heat was
radiated into the frozen ground, before it ever reached her house.

My question is, once I expose the pipes completely, what is a good
method of insulating pipes in sandy and wet soil. Cutting the pipes are
not an option, thus we need something to retrofit. The insulation must
withstand backfilling, vast temperature changes, and moisture. What can
be used on this job?

I built a "box" for pipes going to heat my hottub out of extruded sytrene which can handle 25 pounds/square inch. I cut
strips (1 wide for the bottom, 2 narrow for the sides, wide for the top) using a long straightedge and a very sharp thin
bladed knife, and glued them with construction cement which was compatible with the foam. I believe the foam is R5/inch.

Bob