For many years, there has been a lot of confusion about underfloor heating and wood floors. This is because the answers must be different depending on the flow temperature or surface temperature of the underfloor heating and whether the wood floors are glued.
What can work in buildings or rooms that need less energy may not work in buildings or rooms that need more energy.
Rooms that use a lot of energy or have underfloor heating with high flow temperatures (usually in older buildings): In the past, underfloor heating was usually run at high flow temperatures, and sometimes surface temperatures of 80 degrees Fahrenheit or more were reached.
Building biologists usually advise against underfloor heating for health and room climate reasons (a maximum surface temperature of 70 degrees Fahrenheit is recommended on very cold winter days).
Solid wood floors aren’t a good choice for such conditions because wood dries out a lot in the winter, which can cause big gaps and cracks if the wood isn’t glued together.
Also, underfloor heating under a solid wood floor is slow. It can take 2 or 3 hours for the heat from the underfloor heating to reach the wood floor’s surface and warm the room.
In rooms that don’t need much energy or have low flow temperatures for underfloor heating, which is usually the case in newer or more energy-efficient buildings, underfloor heating can work with very low flow temperatures.
On wooden floors, for example, the surface temperature is often only one or two degrees warmer than the air temperature in the room. When this is the case, people talk about “underfloor temperature control” rather than “underfloor heating.”
This is also fine for health and the temperature of the room. The “sluggishness” mentioned above is usually not a problem when these things happen. Due to the high insulation standard, the room temperature doesn’t drop as quickly, and it takes less time to get the room to the right temperature.
Can solid wood floorboards or floating parquet be put down on a heated screed in a new building?
Since your building doesn’t need much heating energy (KfW efficiency house 70 or better), this is possible if you follow the tips and notes below:
Because of health and environmental concerns, we mostly recommend unglued wood floors, which means no two-layer or three-layer parquet has already been made.
We don’t mind that there are a few more gaps, especially in the winter. Solid wood “works,” which means that it grows and shrinks, a completely natural quality.
If you use wooden floors that aren’t glued down, you should use small wooden cross-sections (widths) for floating installation to minimize gaps and cracks as much as possible.
On the bottom, there should be a click or bracket system that holds the pieces of parquet or plank together. The metal brackets or “clicks” needed for this are pushed into grooves on the underside and hold the pieces of parquet or floorboards together (there are different systems).
It is important to put soundproofing between the screed and the wood floor. So that the underfloor heating or temperature control doesn’t get too slow, it should be as thin as possible (but as thick as needed for footfall noise protection!). This can be done with cork, cardboard, or softwood fiber.
So that the underfloor heating doesn’t move too slowly, the wood floor shouldn’t be too thick. Some manufacturers make parquet floors that can be installed without glue and are as thin as 14 mm. The most they should be is 21 mm.
The impact sound insulation should also be as thick as needed and as thin as possible; 3–4 mm is often chosen.
Run the underfloor heating at the lowest flow temperatures possible, both for health reasons and because higher temperatures can cause gaps or cracks in the floor.
As with any craft work, this must be done according to several rules, including those of the manufacturer.
For instance, the screed and the building site must be dry enough. Also, the parquet or floorboards themselves must be dry enough.
In some situations, you should put up a vapor barrier or retarder. Ask the maker (installation instructions, technical data sheet) or your craftsman about this!
Common mistakes in installing underfloor heating If a wooden floor isn’t floating but is stuck down, an adhesive with as few emissions as possible should be used; with glued wooden floors, the underfloor heating is a little bit faster because there is no need for heat-insulating impact sound insulation.
The wood floor is securely attached to the warm screed, so the heat doesn’t stop moving. Even when not heated, wooden floors feel “warmer” than tiled floors.