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Wood Flooring over under floor heating

Underfloor heating with Kährs flooring

Underfloor heating systems, using electricity or hot water loops, provide a great heating solution. Combined with a wood floor from Kährs, they provide maximum comfort and a beautifully clear living space.

An underfloor heating system should provide efficient and even heat distribution over the entire floor area. The surface temperature of the floor must never exceed 27°C, including areas next to radiators and heating elements, under furniture and carpets, etc. With good furnishings and without too many carpets (or carpets that are too thick), it is reasonable to achieve a temperature of 23°C over the free floor area, giving a room temperature of around 21°C. This assumes that the room requires a normal amount of heating and that seals, insulation, windows, etc. are all of a regular standard.

A few recommendations

Floors with underfloor heating are more susceptible to moisture than floors without. This is because the difference in moisture content in the driest and dampest parts of the floor will increase over time. Underfloor heating causes more extensive drying, which makes the wood contract and shrink. In a cold, dry climate, like the one we have in Sweden, for instance, you can expect to see gaps between strips and slightly concave boards from time to time.

We recommend Kährs Original 15 mm flooring or Kährs Linnea 7 mm flooring, with Woodloc® joints, for use with underfloor heating. Using either of these products reduces the risk of gaps forming.

It’s worth bearing in mind that beech and hard maple wood floors expand and contract more than other wood species. Underfloor heating increases drying, which causes additional contraction.

Installing over underfloor heating

Your wood floor must be laid close to the subfloor, without an air gap. The wood may dry out very quickly if you leave an air gap.

When laying your 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 less than 60% before, during and after laying the floor.

Cardboard is recommended for the intermediate layer, as polyethylene cellular plastic and cork particleboard have a higher thermal resistance.

Requirements when installing underfloor   heating

  • 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 ‘hot 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 doesn’t apply to comfort heating systems, which complement central heating. In this case, the temperature should be considerably lower than the permitted 27°C at the floor surface.
  • The installed floor, including the intermediate layer, must have a low thermal resistance.
  • A vapour barrier must be built into the floor construction and be positioned as close as possible to the wood floor. If the joists are thick or heavy, it is particularly important to have the vapour barrier close to the wood floor. Under no circumstances must the vapour barrier lie on the opposite side of the joist.

  Always check with the product manufacturer or supplier to ensure compatibility prior to ordering your new floor.



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