Besides our savage local climate, another factor in the design was that it be fairly self-contained. The only connection between the floor heating system and the home power is the AC circulation pump, which could be replaced by a DC pump on a solar-charged battery. But since our home power comes from a grid-tied PV system, it's all solar anyhow.
Same goes for the quartz radiant heaters on the ceiling, which are on a thermostat. For extreme cold nights, I use a small propane heater hooked to a portable tank outside.
The water source is four 75 gal. tanks, also passive heatsinks, which get filled with the garden hose, so— no plumbing connection! The water stays mostly at 60°F or above, which the plants like better than our 50° well water. It's nice to puzzle something out and have it actually work.
