Harold Kestenholz
Many manufacturers make electrical heat mats that can be stapled beneath a floor to heat the floor. Then insulation is placed beneath the floor to keep the heat from the crawl.
The same can be done with hot water radiant floor tubing in aluminum heat spreader plates from the many manufacturers than make the products. You can heat the water with an electric boiler or water heater and place controls and circulators on the system to move the water and make the installation safe.
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