I used a 15 gallon hot water tank, heated garage at my other place nicely. One element. Water in tank was heated, when thermostat called for heat, pump came on. Water was set at 150 degrees. It was nice, quiet and fairly efficient. But for some reason the powers that be do not want us using hot water tanks.
It was an open system, running propylene glycol. Worked flawlessly for the 6 years i lived there. I should have done in floor when i poured the new slab here, but i was rushed to get it done.if i add on i think i will do in floor for that part, and use the un approved hot water tank.