Underfloor heating - what power?


The term "performance" of underfloor heating often causes misunderstandings. How to exactly define the performance of a floor heating, and how to determine the actual performance itself, you can learn in detail in this post.

Term of performance for underfloor heating

The performance - or performance - of underfloor heating determines which surface temperatures can occur on the floor. The more efficient the heating, the better and faster the desired surface temperatures can be achieved.

The performance of underfloor heating is technically stated in W / m². This determines which heat output per m² of surface area can be provided by the heating system.

Limitation of surface temperatures

According to DIN EN 1264, the surface temperatures on the floor surface are limited to a certain extent. Technically, the average surface temperatures are used in each case, since a slightly higher temperature prevails over the heating pipes, as between the individual heating pipes.

The permissible maximum temperatures are:

  • 29° C surface temperature in the occupied zone
  • up to a maximum of 35° C in the edge zones (here a little more heat is needed, as more heat can be lost via exterior walls, doors and windows)
  • up to max. 33° C in bathrooms and similar rooms (as there is generally a higher room temperature, usually around 24° C is targeted)

These set temperature limits mean that the underfloor heating only has to provide a limited performance. It therefore often works in the low-temperature range, with flow temperatures below 35° C.

The heat output is currently in the individual areas of a house usually between 50 and 100 W / m².

Performance calculation according to the temperature method (actual power of the heater)

  • underfloor heating
  • second thermometer
  • Aluminum plate for the second thermometer (about 20 x 10 cm in size and 2 - 3 mm thick)
  • stopwatch

1. Determine measuring points

Define three measuring points on the floor covering. These should be evenly distributed throughout the room. Also, set three points distributed evenly throughout the room for measuring the room temperature.

2nd measuring process

Place the secondary thermometer with the attached aluminum plates on the measuring point. Use a small drop of water as the conductive medium between the floor covering and the underside of the tile. Leave the probe at the measuring point for about 15 minutes before reading the value.

For carpets, make sure that you touch the top of the loops with the aluminum plate, but do not press down. The room temperature is measured at a distance of approx. 1.25 - 1.50 m from the ground.

3. form averages

From the three measurement results, form the mean value, in each case an average value for the surface temperature and an average value for the room temperature.

4. calculation process

Subtract the room temperature from the surface temperature. This will give you the value of the so-called overtemperature. If you take this value 11 times, you get the current actual output of the heating in W / m². This calculation is relatively accurate.

Tips & Tricks

Influence on the performance of underfloor heating has both the flow rate and the flow temperature and the spread. In addition, some other criteria for heat transfer play a role. The dimensions of the underfloor heating and the hydraulic adjustment of the underfloor heating must be adjusted so that the necessary heating demand in the individual rooms of the underfloor heating can always be provided.


Video Board: Underfloor heating system. Flushing with GEL Long Life Super Flush 40