TIMBER PRAHA – wooden construction with REHAU underfloor heating

In the Prague-Řeporyje district, unique Timber Praha buildings by UBM Development Czechia have been completed, which are part of the residential complex Arcus City. The interesting aspect of this project lies in several factors. Primarily, these are the first multi-story residential buildings in Prague that are constructed as wooden structures. There are 62 residential units in four buildings (2 three-story and 2 four-story), with layouts ranging from 1+kk to 4+kk, sized from 39 m² to 110 m². Each apartment has a cellar, parking spaces in underground garages, a balcony, terrace, or a front garden. Both the construction itself and the installed technologies contributed to the above-standard comfort of healthy living, as well as obtaining the status of the most energy-efficient homes in category A with environmental BREEM Excellent certification. The original project was created by the architectural and design office Casua, which initially designed a classic load-bearing structure in reinforced concrete. However, it was later decided to implement Timber Praha as a wooden structure, with the project completed by the UBM Development Czechia design office.

Construction from CLT Panels

The load-bearing structure of the wooden building consists of panels made of cross-laminated timber (CLT) that have the required statistical load-bearing capacity. From a thickness of 60 mm onwards, they are airtight and also have the required fire resistance. This is a diffusion-open system supplied by the Austrian company ELK, which has long proven effective in the construction of family homes. The panels were used for all load-bearing internal walls, ceilings, and balconies, and for the first time, they can even be found in the construction of the elevator shaft. The exception is object J, where, for fire safety reasons, the staircase and elevator shaft are made of concrete. The load-bearing walls have a thickness of 140 mm, and non-load-bearing walls are 100 mm thick. On the other hand, ceiling panels are 200 and 180 mm thick (depending on the specific building), while roof panels are 180 and 160 mm thick. The facade is made of a column (KVH beams 60 x 200 mm) frame construction TBF (Two By Four) covered on the inside with fire-resistant plasterboard and on the outside with fibrous plasterboard. The composition is supplemented on the inner side with a vapor barrier, with mineral wool insulation inserted in the middle. Wooden windows with insulating triple glazing (Uw = 0.76 W/m²K) fill the building openings. A ventilated facade with larch cladding is designed on the balcony side. Other parts of the facade are insulated with a contact insulation system, where mineral wool was used as the insulator.

Underfloor Heating with Heat Pumps

Heating and cooling of the apartments in all four buildings (J, K, L, M) is resolved as underfloor heating using technology by the German manufacturer REHAU. The heat source is Aermec heat pumps (ground-water system) with a performance of 39.5 kW for buildings J and K and 18.6 kW for buildings L and M. Heat is extracted from a depth of 199 meters via twenty boreholes. The system includes accumulator storage tanks. The heat pumps are reversible, meaning that in the summer months, the system will be used for cooling the apartments. The underfloor heating consists of a Varionova system board and RAUTHERM pipes with a diameter of 17 mm. The pipes are made of high-tech PE-Xa material, which is peroxide cross-linked polyethylene under high pressure and temperature, giving the pipe excellent properties in terms of strength and durability, which is a welcomed benefit in construction. The pipes are designed for a minimum operational life of 50 years. Years of experience and the quality of RAUTHERM pipe manufacturing are reasons why REHAU provides a 10-year warranty on the material. The floor structure begins with a wooden load-bearing panel covered with a separation foil, on which 60 mm of dry backfill has been applied. This is followed by 30 mm of footfall insulation made of mineral wool and again a layer of separation foil. A Varionova system board was then laid on it, into which the RAUTHERM pipes were fixed. The board was then covered with cement screed. An insulating layer of lightweight foam polyethylene (mirelon) serves to improve the suppression of impact noise under the top layer. The final layer of the floor structure consists of a floating wooden floor. Individual heating circuits are routed to stainless steel distributors from REHAU. The system is low-temperature, which uses the advantages of surface radiant heating that allows for economically heating rooms at a temperature 1 to 3 °C lower than traditional systems without reducing the users' perceived comfort. Additionally, photovoltaic panels are installed on the roofs to support the heat pumps including the heating of domestic hot water, common lighting, and the operation of elevators.

To control all technologies, a Smart Home system – Loxone has been installed in all apartments, controlling not only heating/cooling but also outdoor blinds, energy consumption measurement, videophones, etc. The system includes intelligent moisture monitoring from Sihga, which watches for potential water leaks as well as humidity in the rooms.

Timber Praha by UBM Development Czechia is an example of a meaningful use of the latest technologies, renewable materials, and progressive concepts for building low-energy residential buildings.