nearly Zero Energy Building (nZEB) Herzogenaurach, Germany

In Germany, the “KfW Effizienzhaus 40 Plus” is defined by heating demand of 40 % and transmission heat loss of 55 % compared to the EnEV minimal requirement as well as additional technology equipment. This includes mainly a self-generated energy system, an electrical storage and mechanical ventilation with heat recovery. To demonstrate a more ambitious level, the terraced houses are also designed as plus energy building, which means a negative annual final energy demand including the whole energy balance incl. appliances.

The terraced houses, achieving “KfW Effizienzhaus 40 Plus”, has been monitored for two years from April 2018 – March 2020. The all-electric building is equipped with two central 17 kW ground-source heat pumps (B0/W35), eight decentral heat pumps for providing DHW and a 88 kWp solar PV-system. Beside the buffer storage cascade of 2800 litres and eight DHW-storage tanks of 200 litre each, a 40 kWh battery serves as additional energy storage in order to increase the PV self-consumption. Moreover, decentral mechanical ventilation devices with 86 % heat recovery are installed. The ground-source is used for free-cooling in summer operation. The plus energy balance has been reached in the two monitoring years. The ground-coupled heat pump system achieved an SPF of 5.6 and the DHW heat pumps achieved an SPF of 4.0, while the SPF of the whole energy system is 3.4. Optimized PV operation of the heat pumps led to an increase of the supply cover factor from about 32 % to around 37 %.

Key facts

Case study delivered by: IEA HPT Project (annex) 49