Efficient design

Maximum and minimum acceptable temperatures

The maximum and minimum acceptable temperatures for the internal surfaces of a room are derived from considerations of comfort or surface condensation. UNI EN 1264, based on the outcome of UNI EN ISO 7730 for environmental comfort, suggests maximum surface temperatures for heated floors, walls and ceilings.

For radiant floor systems, UNI EN 1264 sets a maximum temperature of 29°C for occupied areas, and a maximum temperature of 35°C for perimeter areas (with an air temperature of 20°C). In bathrooms, the maximum surface temperature must be no more than 9°C above room temperature (approximately 24°C).
For heated walls, the maximum surface temperature is 40°C, which corresponds to a temperature difference between the wall and the room of 20°C.

For heated ceilings, UNI EN 1264 recommends not exceeding the safe surface temperature of 29°C to avoid radiant asymmetry. The values refer to a room of standard size and shape. A different room of different dimensions may permit temperatures higher than 29°C. It is important to note that the maximum water temperature must take into account the material into which the tubes are inserted. For plasterboard, for example, the water temperature should not exceed 50°C (UNI EN 1264-4).

When in cooling mode, it is important to note that if a surface is colder than the dew point of the room, a layer of condensation could form on the surface. This is to be avoided since it could damage the structure, cause accidents (slippery floor) and make the air unhealthy due to the formation of mould. It is therefore advisable to keep the surface at a temperature above the dew point.

In addition, the minimum temperature for the floor should be 19°C so as not to cause discomfort to anyone in the room, be they seated or standing.