French Parquet ltd supplies engineered parquet blocks and panels.
Please read our notes on the subject of underfloor heating.
Choosing the correct type of parquet
When choosing a floor that is compatible with underfloor heating, it is necessary to check:
1. The thermal resistance and the technical and economic aspects of the parquet;
2. Dimensional stability.
The thermal resistance value varies according to the essence of the wood and the thickness of the parquet floor.
Considering only the small thickness of the parquet, without taking into account the negligible differences related to the essence of the wood, it is possible to establish two categories, based on this size and the type of parquet:
1 - parquet installed by gluing to the subfloor (mosaic, industrial parquet, prefabricated plywood): Thermal resistance R = 0.06 - 0.09 m2K / W, the equivalent of a 4mm carpet;
2 - floating or solid wood parquet (engineered 14 mm or 22 mm solid): Thermal resistance R = 0.15 - 0.18 m2K / W, the equivalent of a 10mm carpet.
Based on this classification and depending on the thermal resistance, we can say that it is preferable (for energy saving reasons) to use a flooring with glued assembly, rather than a floating or solid wood one. For underfloor heating, the latter have lower performance than glued parquet, which has a smaller thickness and better thermal conductivity.
From the category of parquet with adhesive installation, the double layered parquet floor with birch plywood support has the best qualities in use for underfloor heating, because, both its manufacturing technology and its small thickness, ensures:
minimum thermal resistance, which translates into energy saving;
This second aspect is very important. Indeed, the main effect of heating for solid wood elements is that of reducing their humidity, consequently reducing the size and creating more or less important gaps between elements. The engineered flooring, thanks to its birch plywood support, offers maximum dimensional stability and considerably reduces the presence and size of these joints.
For low temperature heating installations (the maximum temperature of the liquid circulating inside the system is 40 ° - 45 ° C), the pipes must be embedded in a conglomerate capable of completely covering them and thus ensuring the best transmission of heat. In most cases, these conglomerates are cement or anhydrite based.
After at least 28 days after its completion (time required by the manufacturer for fast drying binders and anhydrides , the quick drying cycle of the screed can be carried out by starting up the heating system and following the steps described below, so that the percentage of residual humidity required is reached:
1. After disconnecting all the environmental thermostatic probes, which would cause the heating system to operate only conditioned by the air temperature, start the installation by increasing the water temperature by 2 - 4 ° C per day, until it reaches a maximum temperature of 40 - 45 ° C. Initially, the boiler must be switched on at a starting temperature close to the ambient temperature;
2. Maintaining the installation at maximum temperature for 1 or 2 weeks;
3. Shut down the installation by lowering the temperature by about 5 ° C per day;
4. Leave the installation off for 5 - 10 days;
5. Restart the boiler, gradually increasing the temperature;
6. Leave for a few days in operation;
7. Gradual lowering of temperature and shutdown of the boiler, waiting for the installation to cool down.
At the end of this cycle, it will be necessary to check the residual humidity. The screed is dry when the moisture content will be less than 1.7% CM for a cement screed and 0.2% CM for an anhydrous one.
When installing an engineered flooring, a water-free adhesive (two-component epoxy-polyurethane or polyurethane, single-component or two-component, directly spreading on the subfloor) must be used and able to maintain its elasticity characteristics over time.
Usually, the engineered flooring has exceptional dimensional stability performance, even in adverse conditions. The wood, by its nature, is subject to dimensional variations depending on the humidity and the ambient temperature. In order for this natural behaviour not to generate an undesirable effects on the floor, the environmental climate must always be maintained within the recommended limits:
The air temperature should be between 15 and 30 ° C and the relative humidity of the air (especially) should be maintained between 45% and 65%, this range of values corresponding, among other things, to the conditions conducive to normal health and hygiene for humans.
In order to guarantee the stability of the parquet and especially the human physiological demands, the temperature on the surface of the parquet should never exceed 26 - 27 ° C (it should be mentioned that modern installations, operating at low temperature, provide remarkable environmental comfort at floor level from about 24 to 25 ° C).
In order to avoid heat concentrations and, consequently, the appearance of gaps or deformation of the parquet, in addition to a low thermal efficiency, it is recommended not to cover the wooden floors with thick carpets or other materials that have a high thermal resistance.
Bear in mind that pre-laminated engineered flooring, subjected to a particular and intense heating period, may develop slight shrinkage and small joints between the elements, which will disappear once the underfloor heating installation is turned off.
For underfloor heating installations that also have a cooling function, all necessary anti-vapour and anti-condensation systems must be incorporated in order to categorically avoid condensation at any level of the screed composition. The lack of such systems can cause the parquet to absorb moisture and, consequently, it suffers dimensional deformations.
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