Underfloor Heating Temperatures
Since 50 % of the comfort effect is a result of radiation, air temperatures can be little lower with warm water underfloor heating than with other heating methods. As an example an air temperature of 19 degree C feels very comfortable with underfloor heating, i.e. 2 degree C lower than accepted norm with other heating systems. Since 1 degree C reduction will normally save as much as 6 % in energy consumption, a 2 degree C could save 10-12 % on the heating bill.
The temperature of the floor surface obviously affects the rate of convection. If it is only a few degrees above air temperature, the warm air will rise gently and naturally. Compare this to a radiator system where the surface temperature of each radiator could reach 80 degree C to achieve an air temperature of 20 degree C. The velocity of hot air rising from such a radiator would be high, sufficient in fact to create dust laden air currents that encourage draughts. Radiators are inherently dirty, staining walls and prone to creating hot and cold spots within the building they serve.
Underfloor heating is clean, creating low velocity air convection and distributing heat evenly across the entire floor area of the building, eliminating hot and cold spots forever.
By eliminating high velocity convection, underfloor heating cuts out the stratification of heat above head level that prevails with other heating methods. There is no hot air bulge with underfloor heating. The vertical temperature gradient created by the system rises evenly to the ceiling and is almost identical to the ideal gradient.
The elimination of this high air temperature above head level can reduce energy consumption by up to 26% in normal domestic situations.