Dimensioning floor-heating (Power calculations)
When calculating the heat requirement for a floor heating installation you use the same method of calculating as for other heat sources. In average, well insulated houses with a ceiling height of 2.4 – 2.7m and with double-glazed windows an adequate heating is usually obtained, even during cold winter days, with an installed power of 70-100 W/m² floor surface. The exact heat requirement is depending on the geographic location.
Required power in Watt/m² (Guiding principles)
Type of room
Lowest outdoor temperature -20°C -30°C -40°C
Living rooms (except bathrooms)
60 – 90 80 – 110 90 – 120
Halls and entrances
70 – 120 90 – 130 100 – 140
Bath- and shower rooms
90 – 140 100 – 150 110 – 150
70 – 90 90 – 110
Offices and shops
90 – 100 110 –
The maximum over temperature compared to the air temperature that the floor can take (Tgö) is calculated as per below:
Tgö = 0,07 x installed power/m².
Example: Installed power 80 W/m²
Tgö = 5,6 °C.
Studies and experience show that temperatures up to 28°C the floor feels pleasant. With floor heating the temperature should not exceed 28°C.
Higher temperatures can be allowed in places where people stay only a short while, for example in bathrooms.
Most types of flooring materials can be used if the power installed does not exceed 100W/m². When in doubt please consult the supplier of the floor material.
It is not advisable to put an insulated carpet on floor heating, as this carpet has heating insulating qualities.