New nearly zero-energy day care center with energy piles to Vantaa, Finland

City of Vantaa is building a new day care center to replace old one. New day care center is designed for 126 children. Energy efficiency and energy piles have big role in the building. The aim is to build nearly zero-energy day care center with advanced energy saving techniques.

Old day care center in Vaarala has suffered from traffic noise and particulate matter emission. It has also been found to be impractical and expensive to use. Therefore City of Vantaa has decided to build totally new day care center to better location nearby.

Figure 1. Illustration of new day care center (photo: www.vantaa.fi)

The project is a pilot project for new nearly zero-energy building concept of City of Vantaa. All new day care centers are to be built according to this new concept. It is also a pilot project for building information modeling (BIM). The building will have total area of 1500 m2 and estimated costs are 5.4 M€.

“In Finland there are no actual regulations for nearly zero-energy buildings. We set our own target to reduce the total energy consumption of the building to half of the regulations for new buildings”, says Energy Efficiency Specialist Marita Tamminen from Vantaa City Real Estate Centre. “Chosen solutions are based on careful cost and energy calculations. Naturally several different kinds of sensors are installed to verify the actualizing energy consumptions in the future.”

Solar energy and energy piles are utilized to reduce the need of energy. Solar energy is used for heating the water and also to charge heat energy through energy piles to ground during summer time. This charged thermal energy is then extracted from ground during the winter time to warm the building.

Solar energy panels for the project are supplied by Ruukki Construction. Ruukki has vast experience on low energy buildings and especially on energy piles. Heat collecting pipes, other pipelines and equipment for energy piles were designed and supplied by Uponor. Uponor has been involved in almost every energy pile projects in Finland.

Same piles working as load bearing and energy collection

Total amount of piles is 137 of which 54 are energy piles and equipped with heat collecting pipes. The minimum distance between energy piles is 3 meters. This is why it’s not economical to put heat collector pipes to every pile. Eight of the energy piles are not supporting the building, those piles are located to the floor area of the building, where distance between bearing piles is much larger than 3 meters.

Utilization of steel pipe piles to work as energy piles doesn’t mean big changes to pile and foundation structures. Structural and geotechnical resistances of piles remain the same. Only differences in piles are bearing plate with hole for heat collecting pipes and internal grouting. Internal grouting enables transition of heat energy from soil to collector pipes.

Figure 2. Driving of steel pipe piles, installation was done by Suomen Teräspaalutus Oy

Usually the length of energy pile should be at least 15 meters. Pile lengths in Vaarala day care center are approximately from 14 meters to 20 meters and the average length of piles is 18 meters. The length of each energy pile was sent to Uponor and heat collecting pipes were prefabricated at Uponor’s workshop to fit exactly to each pile. Also the energy calculations were updated to match actualized lengths of piles and heat collecting pipes.

Figure 3. Installation of heat collector pipes to piles

Heat collecting pipes are making a double loop inside the energy piles. With double loop there are four heat collector pipes inside the energy pile, but only two pipe heads per pile needs to be connected.

Figure 4. Due to double loop there are four heat collector pipes inside the energy piles

Figure 5. Heat collector pipes installed and ready for further connections

Main contractor of the project, Rakennus Future Oy, sees that energy piles cause no problem for other construction works. “Installation of heat collecting pipes needs only little extra scheduling, but that is not a problem”, says Kari Tasanko, site manager of the project, “Modern buildings contain so much technical installation, the increase for that is very small”.

eRR and eRD energy piles

SSAB’s steel pipe piles can be used to collect energy stored in the ground and bedrock. Traditionally, the heat collecting pipes of ground source heat solutions have been installed either in energy wells drilled into bedrock or horizontally in topsoil. If the building site requires piling, SSAB’s steel pipe piles allow installing the heat collecting pipes directly inside steel piles installed in the ground without extra excavation work or drilling of energy wells.

The energy pile system is especially suited for buildings that need both heating and cooling. In their case the system keeps the thermal balance of the soil suitable for energy production for decades.

Energy pile products

Nearly all sizes of SSAB’s wide range of RR and RD piles can be used as energy piles. Driven RR piles and drilled RD piles can be used as energy piles as such without major changes.

The drilled eRD energy pile can be implemented, where necessary, also as a so-called hybrid pile solution where a deep energy well is drilled through a pile installed to bedrock.

• The accessories of eRR and eRD piles are the same as those of RR and RD piles with the exception of the bearing plates:
• The tip of the eRR pile is protected by a bottom plate, a rock shoe, etc.
• The tip of the eRD pile has a normal drill bit
• Piles are spliced using SSAB’s reliable and easy-to-use mechanical splices or by welding
• Penetrations are made in a standard shaped bearing plate to enable installation of heat collecting pipes through it

eRR and eRD piles are installed just like RR and RD piles. The only new work phase is the installation of heat collecting pipes inside piles after piling.