Passive self-regulation for underfloor heating

Although underfloor heating systems are used in association with temperatures controls with different degrees of sophistication, the underfloor heating system provides its own passive self regulation.

Floor temperatures are slightly higher then those of the room air. A rise in air temperature due to solar gain or increased occupancy means that the air will soon become as warm as the floor.

As soon as this point of equalisation is reached the laws of physics dictate that there can be no further heat emission from the floor. The effect is as if the system was shut down. The process is rapid and precise. Heat emission from the floor will begin to decrease as soon as the air temperature rises. Given an air temperature of 20 degree C and a floor temperature of 23 degree C heat emission from the floor will decrease by one third for each degree of temperature that the air temperature rises.

A three degree rise in the air temperature would thus be sufficient to neutralise the underfloor heating system completely.  Theoretically, this in-built self-regulation makes possible to design and install underfloor heating with no form of room temperature control in the shape of thermostats or valves.  In practice the floor temperature must be controlled in order not to exceed the room temperature, so programmable digital room thermostats are needed for the underfloor heating system.

As mentioned before, floor temperatures should be kept within a certain range of 19 – 26 degree C for the highest comfort, although no higher than 29 degree C. If there is no room temperature control the underfloor heating system will indeed balance itself when the floor temperature reaches the temperature of the surrounding air. Nevertheless the floor will reach the same temperature as the circulating water, which result in uncomfortable temperatures and energy waste.

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