BKT system REHAU heats and simultaneously cools

We live and work in an era of sophisticated heating systems, which not only serve their basic function but also contribute to environmental protection and provide users with a healthy indoor climate. It is therefore likely that we are on the brink of a massive expansion of a heating and cooling system called BKT, or Beton Kern Temperierung. The principle of this system lies in tempering concrete ceiling structures. It is a natural phenomenon of heat, or cold, accumulation in massive concrete with a high volumetric density, which further radiates into the surroundings, meaning into the rooms. This phenomenon can be compared to the effect of a church, which, thanks to its up to one-meter-thick walls, manages to maintain a pleasantly cool environment even in the hottest summer and vice versa. However, since such thick walls cannot be built for many reasons today, a similar effect is created with the help of hot water pipes, in which the heat-carrying or cooling medium flows as needed.

Two Systems: BKT or oBKT

Two slightly different systems are used for tempering concrete ceiling structures. The first is the aforementioned BKT system. The RAUTHERM S pipe with a diameter of 17 or 20 mm is laid in the center of the concrete slab between the lower and upper reinforcement mats, with a pipe overlap of 100 mm. The pipe is fixed with a spacing of 15 cm using a prefabricated module made to measure according to the specific project. This solution is the most suitable for accumulation effects, but one must account for a relatively small reaction (10 W/m²h, meaning the surface temperature change is about 1 °C per hour). The heating or cooling capacity is around 37 to 40 W/m². The temperature of the heating medium is usually around 32 °C (depending on other factors such as the type of insulation, etc.). The second system is called oBKT, which prioritizes the speed of heat transfer compared to the first. The reaction and surface temperature change is around 2 °C per hour. This is due to the fact that the pipe is placed just below the lower reinforcement of the concrete core (about 17 mm). The prefabricated modules are similar. The pipe is fixed in a double meander, but a RAUTHERM SPEED pipe with a diameter of 14 mm is used with a spacing of 7.5 to 15 cm. The heating or cooling output is higher, specifically 47 to 60 W/m². Again, it depends on the spacing and the design of the concrete ceiling.

In both cases, the same pipe material is used, which is cross-linked polyethylene type PE-Xa, known for its excellent surface durability and strength. The quality of the entire system is also contributed to by the technology of the pipe connections, which is a REHAU specialty in the form of the sleeve method (developed by REHAU back in 1985), which is the safest of all systems. Since this is a low-temperature heating and cooling system, the ideal energy source is a heat pump with a cooling module. It would be hard to find a more efficient and economical way of heating. It is no wonder that the number of implementations increases every year, and it is even interesting that not only in the field of commercial construction. The BKT system is also finding its way to private investors in the construction of apartment and family houses. However, for illustration, we will mention one of the latest completed projects, which was the expansion of the FSV UK library in Prague's Jinonice (oBKT system, the project author is the APRIS 3MP studio), or the new construction of a kindergarten in Semily (implementation by MBQ, s.r.o.).

For more information, visit www.rehau.cz