Can Heated Underlayment be used as the primary heating source?
Yes it can if the total Watts installed meet your BTU requirements (1 Watt = 3.413 BTU’s). Generally, you need to cover as much of the floor as possible to maximize your BTU capacity to heat the air space above the floor. Room insulation value is also a very important factor. A room with average insulation will take twice as long to warm up as a room with good insulation.