"twfsa" wrote in message

If you are using a boiler to heat your home, and are going to replace the
driveway a manifold type control to limit the amount of warm water that
would be circulated thru the driveway seems the way to go, it does not
have to be heated to 70degs, once warmed the concrete should hold the
heat.I would think 35 degs would be sufficient.

If you use the boiler, you'd have to go to a glycol system or drain the
lines when not in use. I don't think that would be the most practical
system.