Mr buddy heater

Was thinking of going sort of hydroponic using hot water heater. We have under slab heating in the s/b. Since it is mainly at night when we get chilled, was thinking about putting hydroponics pex with a thermostat controlled zone control valve attached to the underside of the bed and a second water pump for circulation. Could cut into hot water line in bathroom and mount pump there so noise is minimal. propane use would be minimal. I find furnace cycling drives me nuts when trying to sleep so could turn down at night and turn bed down during the day.