Main content:
Refurbishment of a listed residential building in Freiberg, Germany
Project participants:
Client: Dr. Holger Neuhaus
Architect: Uwe Gerschler
Energy planner: Institut für Bauklimatik, TU Dresden
Gebäudedaten:
Building type: residential building
Location: Donatsgasse 21, 09599 Freiberg
Gross floor area: 396 m²
Jury evaluation
"The conversion of a small 500-year-old listed residential building into a zero-energy house impresses with its integrated concept that also respects fundamental conservation requirements. The unheated access area at the front of the building means that energy-oriented refurbishment of the historical facade which faces onto the street was not necessary here. Even though the plan for a seasonal thermal storage tank for the 20-m² solar collector array is not very convincing from an engineering point of view, the high-quality interior insulation with favourable properties, the double windows and heat recovery all combine to bring the heating requirement close to passive-house levels."
Project_characterisation
Building concept
The historical character of the building is to be preserved as part of this refurbishment project. For example, the gneiss wall with window openings at the front is to be exposed and will remain visible to the residents. The entrance area is generously proportioned, and prepares the inhabitants for the coexistence of the old and the new. To improve the living space, the extension’s monopitch roof is to be raised and a flat roof planted with vegetation is to be included. In addition, it is planned to divide the building into three separate residential units. Depending on the domestic situation, these apartments can easily be combined to create one spacious city apartment. The separate apartment is wheelchair-accessible. The rear windows of the building look out to the northwest, meaning that a view of Freiberg and the presence of the garden are both integral parts of the living experience. The top-floor apartment with its 80-m² roof terrace is particularly charming.
Energy concept
The refurbishment is to preserve the historically significant building fabric, and will also fulfil contemporary standards for building and living regarding energy-savings and resource-conservation. This is to be achieved by the following measures:
Orientation towards passive-house standards, insofar as possible: Components and measures are used that are familiar from passive-house building, such as the reduction or removal of thermal bridges in old buildings, the insulation of external walls (target: U < 0.1 W/m²K), window units that are compatible with passive-house standards with double glazing (particularly suitable with the deep window recesses in old buildings), air-tightness, and a ventilation system with heat recovery. The heating energy requirement is to be reduced to 24 kWh/m² p.a. with these measures.
The use of waste heat from domestic water: Warm wastewater is collected in a biological treatment basin in the heating room. The water cools down to room temperature, and the heat released is distributed throughout the house via the ventilation system. The heating energy consumption can be reduced by around 6 kWh/m² p.a. in this way. The water can then be used in flushing toilets. Beforehand, it is routed through the underfloor heating for the atrium, which is not temperature-controlled, and thus also transfers some of its heat to this room. The continuous low-temperature heating provided in this way helps to avoid the formation of mould and also improves the thermal buffering effect for the main building.
Solar thermal heat generation: 20 m² of south-facing roof area with an inclination of 43° is available for solar thermal energy. The use of solar energy is fully integrated into the roof envelope, meaning that it also forms part of the roof cladding.
Photovoltaic power generation: In addition, a roof-integrated photovoltaic system contributes to the balance by supplying the building’s electricity requirement. Around 30 m² of dormer window area is available for the photovoltaic unit. Full roof-integration and a common mounting system for the solar thermal system and the photovoltaic equipment result in an aesthetically attractive appearance for this listed building.