The first known heat exchangers for homes were just rocks placed inside a fire. The rocks would store the heat from the fire and were then moved inside of a hut or small tent to warm the inside. The heat that was being lost from the fire was being captured by the heat transfer surface, the rock, and then used to heat the inside of the home.

The first “central” home heating was invented by the Romans, though there is evidence that Indians may have been using this type of “hypocaust” technology millennia earlier. The premise involved a basement room located under the main floor. The floor was made with cement sandwiched between layers of tiles on the top and bottom. Space was left for hot air and smoke from fires in the basement to travel through the flooring so heat could radiate up into the room.