Heating screed
The heated screed is a mineral screed floor structure that is provided with heating elements and is used for underfloor heating . Alternatively, heated screeds can also be made with mastic asphalt .
history
After the knowledge about the heatability of floors was apparently initially lost after Roman times, heated screeds were not used again in Germany until the 1970s. Helmut Unger pioneered this technology as a pioneer. In his technical article "Screeds and underfloor heating" he highlighted the status of heated screed technology and, as chairman of the "Heat screed" working group at the BEB and as head of numerous seminars, devoted himself to the development of heated screed in Germany.
Use as underfloor heating
"Heating screeds" are those structures that contain heating elements either in or below the load distribution layer. The screed acts as a radiator and warms the room. This is explained by the fact that for people at a room temperature of e.g. B. 20 degrees Celsius, a surface temperature higher than 20 degrees Celsius is necessary to feel comfortable.
In addition, the use of underfloor heating allows the planner to forego any radiators that may interfere with his design , which extends the design options.
Different versions
Pipes filled with hot water or, alternatively, electric heating mats are primarily used as heating media. In the majority of systems, the pipes are located in the screed cross-section, while the heating mats are often located below the screed slab. Of course, you can also embed this in the middle of the screed, but here you run the risk of the heating mat acting as a separating layer if the subsequent layer of screed is not really "fresh-on-fresh".
If only a floor tempering z. B. is provided in bathrooms, it is also possible to place the electric heating mats below the tiles and thus above the screed. But then one no longer speaks of a "heated screed".
For a faster reaction of the heating system, there is the possibility of installing underfloor heating with a click. This consists of dry screed panels with a prefabricated milling that fixes the heating pipes. This system combines the previously separate components, dry screed panels and underfloor heating, from earlier systems.
disadvantage
Compared to conventional radiators, underfloor heating has the disadvantage that it takes longer for the room to warm up, which limits the ability to regulate quickly to a certain extent. Attempts are being made to compensate for this deficiency by making screed structures that are thinner and therefore quicker to heat up. In addition, the way of laying the heating pipes more densely than before in many systems is being used, or so-called “climatic floors” are chosen, which enable the screed to be heated evenly with a plate that carries the heating medium.
planning
Before laying the insulation boards, it is necessary to check the subsurface, install any vapor barriers / seals that may be required and make a leveling . It is therefore advisable to plan the laying of the insulation panels in the performance range of the screed layer, as he is prepared for this work.
In this context, for. B. a system can be selected in which the screed layer brings the insulation panels including cover. The heating engineer then lays a grid that is used to fasten the pipes. Alternatively, the pipes can also be attached to a solid base above the insulation layers.
Due to their practical experience, some planners give preference to systems in which no high / low structure is created within the screed, as is the case with some studded panels. The latter can promote the development of tension within the screed cross-section, and in some systems the connection to the edge strips is not appropriately solved.
When the screed is laid, the heating pipes must be filled with water in order to detect any leaks in good time. The water temperature in the heating pipes should correspond to room temperature; only in winter can a flow temperature of 20 degrees Celsius be used for frost protection purposes. When placing screed, special care must be taken not to damage the heating pipes. The screed must be divided into sub-areas, otherwise there is a risk of cracks in the screed. The joint plan should produce as compact shapes (rectangles) as possible. The heating pipes must be protected in the area of the joints.
execution
As a rule, heated screeds should be applied as flowing screeds. When it is heated up, the screed expands in all directions. It is therefore of fundamental importance for heated screeds that they do not come into contact with rising components such as walls and / or columns. The edge strip should be dimensioned a little thicker than with conventional floating screeds. A border strip thickness of 1 cm (normal is 0.8 cm) is recommended in any case, although this also depends on the type of screed. In exceptional cases, even thicker edge strips may be necessary if the rooms are particularly large or the temperature spread is extreme.
In the case of underfloor heating, the thermal resistance of the floor covering, including any underlay, should not exceed 0.15 [m2 x K / W].