This "house within a house" is set to become the first energy-self-sufficient residential building constructed inside a listed building on a typical Altenburger four-sided farm.
The sun barn is being built on the south side of the Vierseithof Plottendorf historical farm, one of Thuringia's cultural landmarks and the last remaining farm flanked by buildings on all four sides in the district of Plottendorf. The old barn, which was previously used as a threshing house and stable, is being completely revitalised using environmentally friendly building methods by converting it into one of the first energy-self-sufficient houses constructed inside a listed building. The sun barn will take two years to build, with completion planned for summer 2018.
The barn's volume is larger than the surface of the residential building being built inside it, meaning that the concept of a "house within a house" seemed perfectly apt. The thermal envelope of the heated area of this residential building is therefore located on the inside. The spaces between the barn's existing exterior walls and the walls of the interior residence create an unheated thermal buffer. The interior house only adjoins the exterior wall on the south side of the building, where a large area of the facade is being opened up and fitted with glass panels in order to tap into passive solar energy. The design was put together by the architecture firm of Claus Krüger in cooperation with the building's owners. Claus Krüger has many years of experience in sustainable and environmentally friendly construction, and sits on the board of the Saxony Chamber of Architects. He is also an official energy planning expert for the government-owned development bank KfW, as well as for the Federal Office for Economic Affairs and Export Control.
Thanks to the excellent standard of insulation, and the outstanding level of airtightness in the interior house, there is a low remaining heat demand, which is covered virtually all year round through the use of solar thermal energy and its long-term storage. The additional solar power and its on-site use via a battery storage system enable the building to become an energy-plus house that meets both the "passive house" standard as well as the "solar house" standard, with a self-sufficiency level of 85%. Professor Timo Leukefeld aided in the design of the energy supply facilities. The pioneer of solar-powered housing constructed the two first energy-self-sufficient family houses in Freiberg and is an "energy ambassador" for the German government.
Another special feature of the sun barn is the equally self-sufficient process for disposing of waste water, which is released directly into a body of water from a fully organic small waste water treatment tank, which operates without the need for its own power supply.
The concept of energy-efficient and self-sufficient construction in a listed building points to a move towards the sustainable conversions of existing buildings and therefore helps to limit the consumption of valuable undeveloped sites.
The daily land consumption rate in Germany is currently around 73 hectares, which corresponds to an area larger than 100 football pitches put together. This considerable loss of natural areas not only threatens biological diversity — it also leads to a daily increase in infrastructure costs. Therefore, the German government has declared that it is its aim to strictly limit the daily land consumption rate to a maximum of 30 hectares per day. The allocation of greenfield land—particularly in the shrinking rural areas of Central Germany—to further new housing developments is therefore incompatible with this commitment to sustainability.
Revitalising an existing barn by turning it into an energy-self-sufficient residential house is one example of future-oriented, sustainable development. By protecting a historic building structure using modern, environmentally friendly construction methods and using renewable sources of energy, the sun barn helps to reduce the rate of land consumption.
The project has received the support of a funding initiative for integrated rural development and the revitalisation of brownfield sites. This programme involves the participation of the state of Thuringia and the European Union within the framework of the European Agricultural Fund for Rural Development (EAFRD). Funding is provided by the region's office for rural development and land reorganisation, based in the city of Gera.
The scheme sees Europe and the state of Thuringia invest in the rural areas.