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Heat pumps a winner: Daikin Europe N.V.’s net zero energy building project one year on

In 2010, Daikin Europe N.V. announced its intent to join forces with major European research institutes to develop economically feasible net zero energy building (nZEB) concepts based on heat pumps. A test nZEB was constructed in the Ruhr region of Germany, and at the end of February 2012, a balance was made of the building’s performance after one full year of use. The result: the building generated more energy than it used, while at the same time providing optimum comfort for users year round.

The nZEB concept 
A net zero energy building is defined as a building that is energy neutral over a period of one year. It must deliver as much energy to the supply grid as it uses. The two-floor test building, constructed in Herten, Germany, houses a single floor warehouse and two floors of office space. Since the idea was to start with an open and flexible architectural approach, the building envelope did not target extreme insulation values, but rather a slight improvement in the German EnEV standard, in combination with measures to reduce the loads such as controllable solar shading on the facades and windows, cool roof covering, and a free cooling option in the heat recovery ventilation system. 

The next step is to reduce to a minimum the energy consumed by active systems. Floor heating is provided by a Daikin Altherma air-to-water heat pump, with leaving water temperatures set in function of the outside temperature. Cooling and dehumidification in the summer is handled by a Daikin VRV III air-to-air heat pump, with each office receiving an indoor unit for individual comfort control. Ventilation is provided by two Daikin VAM heat recovery ventilation systems. 
The final step in the nZEB concept is to generate energy within the building to compensate for any energy used by active systems such as heating, cooling and lighting. In this project, thin film photovoltaic panels were mounted on the roof, with their efficiency augmented by the use of Daikin’s durable sun reflective Zeffle coating.

Objective testing
Five European research institutes were part of the project to measure in detail the energy efficiency as well as comfort for users: Fraunhofer Institute for Environmental, Safety, and Energy Technology Umsicht, Fraunhofer Institute for Building Physics (IBP), Technical University Dortmund, CETIAT in France, and the University of Manchester in the UK. Energy efficiency and comfort were measured on the coldest days of winter through the hottest days of summer. Sensors were placed at various heights to ensure detailed results. These measurements were augmented with spot checks and surveys of the building users.

The result: positive net energy balance after one year
After 12 months in operation, the building demonstrated a positive energy balance of 977 kWh. The participating institutes confirmed the results. Hans Erhorn of Fraunhofer IBP: "The nZEB goal was achieved in the monitoring period. A total of 38.5 kWh/m ² electricity was generated by the photovoltaic system during the year, while the total annual energy demand of the building – which includes heating, cooling, ventilation, domestic hot water production, and lighting – was 36.7 kWh/m²"

Heat pumps played a major role in the project’s success. Peter Schwerdt of Fraunhofer Umsicht: “Air-to-water and air-to-air heat pumps are well suited to the nZEB concept. Their flexible operating modes ensured a comfortable indoor climate with the best energy efficiency.” The building comfort aspect was also underscored by Anne Tissot of CETIAT: “Even though important energy saving measures were realised in Daikin’s nZEB, indoor air quality and thermal comfort were excellent throughout the year.”

For more information on the full range of Daikin heat pumps, visit