When TV channel Canal+ wanted to create a comfortable indoor environment, with a system that would meet strict energy performance criteria, France Energie stole the show with its UtCi 4in1, mini-reversible heat pumps. The new Canal+ head office covers some 42,000 m2 in the iconic Sways building, Issy-les-Moulineaux. The project has innovation and energy efficiency at its core, being rated at an impressive BREEAM level "Excellent", NF HQE "Exceptional", BBC Effinergie, E2C1 and R2S 3 stars.
With the HVAC system central to energy use, the indoor environment and staff productivity, more than 1,500, UtCi 4in1, mini-reversible heat pumps were installed on water loop, to provide heating, cooling, ventilation and heat recovery.
Key to the project requirements was the ability to simultaneously heat and cool individual rooms, improve acoustic performance and ensure excellent indoor air quality. The system would also have to help achieve high energy efficiency targets and offer flexibility. Developer, Bouygues Immobilier, had already implemented France Energie's UtCi 4in1 solution on two other projects, and could see the benefits for the Sways building.
The 4in1 UtCi - or Individual Comfort Thermodynamic Unit – uses R513A as a refrigerant and is certified by Eurovent Certita Certification. The reversible water/air heat pumps were connected to a water loop, in a two-pipe system. Each heat pump draws or returns heat to the water loop, depending on the end user requirements. Each of the 1500+ heat pumps operate independently, with the ability for units to be in cooling or heating mode simultaneously. To enable this, the water loop must be maintained between a strict 16 and 21°C to provide both heating and cooling, or between 21 and 38°C in the summer, when all the heat pumps provide cooling only.
In the cooler months, additional heating is provided by a substation connected to the CPCU network. In the warmer months, two roof installed adiabatic air coolers provide additional cooling. But that’s not all, the system has another energy saving trick up its sleeve. The Sways building’s basements are under the water table. Floodwater from the basement has a year-round temperature of 14 to 16°C, and is used to cool the water loop via a heat exchanger. This covers an impressive 25% of cooling capacity, to provide a significant amount of free cooling in the summer.
In mid-season, when there’s a mix of cooling and heating requirements, the system can work without any external energy inputs. Heat pumps working in cooling mode return their waste heat to the water loop, to supply units providing heating. Depending on outdoor temperature and end user demands, the system can be self-sufficient from a third to two-thirds of the year.
Mr. Mousset, project manager at France Energie, explained, “A heat pump is installed in each room to provide heating or cooling for optimum comfort in each office. All the water loop heat pumps are connected to a closed water network that circulates throughout the building, pooling all the heat, so nothing is lost. The overheated offices send their heat back to the offices requiring heating.”
Each UtCi 4in1 serves an area of 15m², providing a fresh air-flow of 30 to 32 m3/h per person. The heat pumps include a double flow ventilation unit, with a heat exchanger for heat recovery. Installed against the exterior walls, each unit is connected to an air intake and exhaust grille. The Building Management System (BMS) controls motorised dampers, for when ventilation is not required.
Internally, the upper part of the UtCi 4in1 unit blows conditioned fresh air into the room. The lower part of the unit draws in the return air. Heat recovery takes place from the return air via a heat exchanger, which cools or heats the incoming fresh air before it passes over the heat pump's main heat exchanger.
Mr. Mousset, continued, “These UtCi 4in1 models integrate a heat pump on a water loop and an air renewal module through the façade. The advantage of this model is its compactness and the elimination of ventilation networks, which allows the buildings to be kept with their existing floor pitch while offering a ceiling height of 2.70m. This is the international standard for comfortable office space.”
The use of certified products was vital to achieving energy efficiency targets and several energy labels. Mr Moussett concluded, “In this building, our UtCi 4in1 ARO16 models are installed and the thermodynamic part is NF PAC certified. As these modules are technically independent, we were able to certify the thermodynamic part. The NF PAC certification reassures investors but also allows 100% of the heat pump's performance to be taken into account in regulatory calculation software and helps in obtaining labels including HQE and BREEAM.”