Improving energy efficiency in old buildings

About one third of German primary energy consumption is used for heating purposes. Old, centrally heated buildings are notorious energy wasters with a heat energy consumption between 160 and 300 kWh/m²a. Improving the energy efficiency of old buildings therefore holds great potential in saving energy which is not only of benefit to individual occupants, but also to the environment. To find a solution which combines maximum energy saving with the greatest possible comfort for the user and minimum investment and operating costs is the objective of an EnBW project in Wiesloch. The following variants are tested:

• One building will be equipped with a conventional central gas heating system with standard radiators and with an optional regulated exhaust air system.

• The heat supply in the second building will be implemented with the help of air/water heat pumps which use the external air as an energy source. The construction outlay and thus the cost for this variant is very low. The installed air/water heat pumps even operate effectively at temperatures of -20 °C. In addition, the central exhaust air system uses the exhaust air as a heat source for the heat pump. The central heating system with standard radiators has been so designed as to achieve good inlet temperatures for the heat pump.

• The third house in the project uses a heat pump with geothermal heat probes as the source of energy.

• The fourth house will function as a reference object and will be equipped with a decentralised system. The house will be heated by a ventilation storage heating system with heat recovery. The ventilation unit of the device ensures continuous, adequate ventilation. A decentralised warm water system with an electronically controlled electric heater and a central solar preheating unit complements the decentralised heating concept.