So just on the house do you see any heat savings. Did you put separate thermostats in major rooms? I was looking into tankless hot water too.
I'm sure there are plenty of savings. It's the most efficient system I could design. I don't make more than 120 degF HW for heating, and bump it to 140 degF for Snow Melting and DHW requirements. All the heat is instantaneous. It's a "0 Mass" system, so all the heat goes to it's intended locations. My boilers are 99% efficient condensing boilers because of my low temp capability. Radiant heat is a perfect matchup to condensing boilers for that very reason. A cast iron boiler can't be used in a condensing mode as it will rot out from the condensed flue gases.
Extremely difficult to measure the savings with the fuel costs all over the place the last few years. When I first put it in, my bill didn't change cost wise, but that included many snow melting days as well. The way I see it, I operate that snow melting system for free, compared to the operating cost of my old CI steam boiler with CI radiators!
I have a thermostat in EVERY ROOM. Each room is a zone. I also have 24 loops in 2 zones of Snow Melting with automatic sensors to turn the system automatically when it snows.

Hoist!
