Passive House Case Study Hannover-Kronsberg, Germany

Passive House Case Study Hannover-Kronsberg, Germany

This case study looks at the 32 terraced passive housing project in Hanover Kronsberg built in 1998 by the developer Rasch & Partner in cooperation with the Stadtwerke Hannover. For the first time a heating system using exclusively post heating of the fresh air necessary was used. This very simple and cost efficient house technology concept is possible thanks to extremely high building envelope efficiency with very good insulation, thermal-bridge free construction, airtight building element junctions and windows of a quality not previously available. Together with the heat recovery system, this leads to a space heating requirement in the houses of less than 15 kWh/(m²a), a figure which is roughly a seventh of that used in typical new German housing.

The houses are arranged in four rows with eight houses in each row. This arrangement offers the advantage of reduced envelope surface area to volume ratio. This project was unique at the time and the main intention of this project was to show, that heat supply in passive houses can be realized by warming up the supply air of the balanced ventilation system. These houses have no conventional heating system with radiators, except one in the bathroom.

Passive solar

The main windows are directed to south, so daylighting is provided by direct solar radiation for the duration of the day. In winter, solar gains through windows cover about one third of space heating energy demand. In summer, a manual-driven shading system protects the rooms from too high temperatures. Besides this, the high quality thermal insulation in combination with the large internal masses (concrete) help to keep the temperatures in summer on a moderate level, if cross ventilation during the night is applied.

 Construction

The walls and roofs are made of light-weight wooden construction with Uvalues of Uwall= 0.13 W/(m²K) and Uroof = 0.10 W/(m²K). The core of the building, the cross-walls and end-walls are made of prefabricated concrete elements. In addition, triple-glazed windows with specially insulated window frames as well as a home ventilation system with a high efficiency heat exchanger were installed.

Thermal Image of Passive House

The roof is built from prefabricated lightweight wood elements with 400 mm high I-beams, which span from one partition wall to the next. An internal polyethylene foil forms the essential airtight layer. The outer wall elements for the north and south facades are also built using prefabricated lightweight wood elements. So-called half box beams are used as shafts. An internal polyethylene foil forms the airtight layer. The outer wall of the gable sides is, like the house partition walls, built from loadcarrying reinforced-concrete slabs. This is protected on the outside against heating losses by a 400 mm polystyrene external thermal insulation compound system. The

Thermal Bridge Free Eaves Junction

concrete itself forms the airtight layer for the gable wall. The floor slab consists of 240 mm prefabricated steel-reinforced slabs, which is insulated underneath by factory-made 300 mm polystyrene external thermal insulation. The concrete floor itself also forms the airtight layer. Only the exhaust and intake ducts in the gable area and the drainage pipe through the base plate penetrate the thermal envelope. The ventilation system and the supply pipes run to the building services container in the gable area of the houses.