House between the apple trees has reached the underfloor heating installation phase. The team of carpenters from Litarh finished the job, basically completing the project from a structural point of view and all the builder's tasks. Now it was the installers' turn. The actual construction took a month and a half, with the rest of the time needed for the design, approvals, foundation, installations and finishing touches. During this phase of the construction we spoke to Cristian Tanase, who is in charge of all the thermal installations, including the underfloor heating. You can watch the episode at the end of the article. But until then, a few thoughts on the efficiency of underfloor heating. There are voices that say it is not recommended to choose wood when having this type of heating because it is a good insulator and makes the system inefficient. Let's see what the experts say about wood and underfloor heating.
Heat resistance of wood flooring
Heat resistance is the main factor influencing the efficiency of underfloor heating. It affects heat transfer from the installation to the room. Lower heat resistance means shorter heating time. Wood has a higher resistance to heat transfer, which means an increase in the time the room heats up. But the same heat resistance means that when the installation is switched off, the heat lingers longer. Wood also stores heat energy and releases it gradually compared to other materials, contributing to long-lasting warmth.
Heat resistance is directly proportional to the thickness of the material, being lower if the material is thinner. On the other hand, the thermal conductivity of wood increases with its density. So for efficient heat transfer, the wood of the floor must be thin and dense. The thicker the flooring, the lower the efficiency and the higher the energy consumption. The heat resistance of the floor should not be higher than 0.14 m²K/W. As each layer has its own heat resistance, it is recommended not to lay carpet over the wooden floor as it will decrease the heating efficiency.
Factors on which the efficiency of wood floor heating depends
Wood's resistance to heat transfer is not the only problem with underfloor heating. Its dimensional variation with humidity variation can be another problem. This can mean shrinkage with gaps between the elements, expansion (the floor swells) and warping (twisting, bending). All this must be taken into account when installing heating systems under a wooden floor.
To avoid surprises, the wood needs to be heated evenly, which is why heating must be installed evenly under the entire floor. The installation must be done on the basis of a project drawn up by a specialist who will also make recommendations on the type of flooring and positioning of furniture. Furniture should also have legs to allow air to circulate underneath.
The parameters under which the installation operates must be rigorously controlled. The temperature under the wooden floor should not exceed 27ºC. In this case the surface temperature of the floor will reach 23-24ºC and the temperature in the room 21-22ºC. To maintain this level, the house must be properly insulated. If a higher temperature is desired, underfloor heating will have to be backed up with another heating option. The most efficient underfloor heating is ceramic (tiles) or stone.
The thickness of the wood should be no more than 18 mm. A thicker wood will behave as an insulator and heating will not be more efficient. A 14-16 mm thick floor is most efficient.
The wood must be adequately dry and its moisture content in the range 8-10%. Dried wood performs best in professional dryers that follow controlled drying cycles.
Types of wood flooring suitable for underfloor heating
Wood is a natural material that "works". Rising temperatures can cause wood flooring to warp and even crack. But not all species react in the same way. Maple and fagul are prone to deformation, while oak tree, bamboo, cherry deform much less. Warping is excluded in layered materials. Deformation and wood movement also affect the finish. The varnish film on a solid wood floor is more likely to crack than that on laminate flooring. The risk is eliminated by using oil or wax-based finishes.
Laminated wood flooring. It is recommended by specialists for this type of heating because it is very stable, adapting to changes in humidity. Laminated wood is plywood or MDF veneered with a veneer of a species suitable for parquet (oak, ash). The plywood can be made of the same type of wood or a lower species. The plywood made of new, seasoned wood (resinous, poplar) is best suited for underfloor heating because it is easy to pass heat through.
Solid wood duvum. Long wooden elements behave differently depending on the grade. Hard, high-density wood is not recommended for this type of heating. It varies greatly in size and can warp or crack. This is the case with beech or maple. Soft, soft, woody wood, such as resinous wood, is not recommended because it blocks heat instead of transferring it. Always seek specialist advice as defects can occur. The thickness of the boards is also very important.
Parchet. This category includes small floor elements. Both hardwood and softwood can be used. It is possible that dimensional variation may result in gaps between elements. This is remedied by repositioning the elements and filling the gap with new elements. The best species are oak and nuc.
Bamboo flooring. Bamboo is increasingly used for flooring. It is twice as hard as oak and performs well in underfloor heating.
Laminate flooring. In this case it is not wood. Laminate flooring is layers of resins, and on the surface is an imitation of the look of wood. Laminate flooring has good thermal conductivity due to its thickness and high density and is an affordable option for underfloor heating.
Before fitting wood over under-floor heating, seek specialist advice. You will avoid a lot of inconvenience.
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