All Kährs floors, except Beech and Hard Maple, are suitable for use with underfloor heating. It is, however, extremely important to follow both our specially designed installation instructions, as well as the instructions and recommendations given by the supplier of the heating system. If properly installed, you will achieve a beautiful and long-lasting wood floor with the increased comfort of radiating a pleasant warmth.
Susceptible to moisture
Floors with underfloor heating are more susceptible to moisture than those without, as the difference in moisture content between the driest and dampest parts of the floor will increase over time. Underfloor heating can cause extensive drying, which makes the wood contract and shrink. In a cold, dry climate, you can expect to see gaps between strips and slightly concave boards from time to time. We recommend Kährs Original 15 mm parquet flooring or Kährs Linnea 7 mm with Woodloc® or Woodloc® 5S joints to achieve the best results.
When laying a floor over underfloor heating loops, the working temperature should be at least 18°C. This is applicable to boards, subfloors and room temperature. The relative humidity (RH) of the air must be between 30 and 60% before, during and after laying the floor. Your wood floor must be laid close to the subfloor and without an air gap, as air gaps can cause the wood to dry out. Cardboard is recommended as intermediate layer.
The electrical underfloor heating system must deliver no more than 80 W/m2, evenly distributed. In a normally insulated house, with a properly functioning underfloor heating system, the temperature of the floor surface is generally 2°C higher than the room temperature. In a hot-water underfloor heating system, the flow temperature is usually 7–12°C higher than the floors’ surface temperature and must, therefore, never exceed 39°C. For any system, the surface temperature of the floor must never exceed 27°C. This also applies to areas next to and above radiator pipes, above pipe runs and under carpets and furniture, etc.
Special installation requirements:
- The floor construction must have a heat-distributing layer that gives an even temperature over the entire surface of the floor area, in order to prevent high temperatures in certain spots.
- It must be possible to control and limit the surface temperature with a high degree of accuracy.
- The entire floor area must be heated. However, this does not apply to comfort heating systems, which complement normal heating.
- The floor - including the intermediate layer - must have a low thermal resistance.
- A vapour barrier must be built into the floor construction, positioned as close as possible to the wood floor. It is particularly important to have the vapour barrier near to the wood floor if the joists are thick or heavy. Under no circumstances may the vapour barrier be placed on the opposite side of the joists.