A@W Newsletter

Building a house in the Black Forest means, above all, taking a close look at the topic of timber construction. In Nordrach, located in a valley not far from Biberach, the owners also placed great importance on the health and sustainability of the building. On this basis, Offenburg architect Michael Welle developed a polygonal-shaped building made of wood, straw and clay, the design of which is based on the typical features of a historic Black Forest house and interprets them in a modern way.

The apartment block in Nordrach stands on the edge of the forest and reinterprets the historical model of a typical Black Forest house. © Michael Welle Architecture, Offenburg

The building with its pentagonal floor plan responds to the conditions imposed by the building site: approximately half of the plot was allowed to be built on. On two sides, the outdoor area statutes define the boundaries; on the eastern side, the course of the eaves is harmonised with the edge of the road. The gable end on the north-east side roughly follows the edge of the slope and looks out over the valley. Half of the gable on the opposite side is orientated down the valley, the other half up towards the edge of the forest. The building echoes the slope with its roof, which is pulled down quite far to provide more protection from the weather. The workshop is located in the striking base made of solid concrete, where some of the finishing elements for the residential building were even manufactured. On the sloping plot, this basement forms a design and structural basis for the building above.

A purely wooden house is built on a solid concrete base, the building materials of which have been processed or treated as far as possible without adhesives or paints. © Jürgen Pollak, Stuttgart

Traditional, modern timber construction

The timber construction, which is placed on the concrete base, was prefabricated in a local carpentry workshop, where the wood was planed, bound and processed into wall, ceiling and roof elements. This meant that the construction time could be reduced to a minimum. In keeping with the sustainable regional concept, the timber comes from forest farmers in the region and was cut and dried in local sawmills. In order to create the healthiest possible living space atmosphere, no unnatural materials were used in the interior. In fact, the wood is mostly left in its natural state, at most partially leached or oiled, for example in the furniture or floors, which are treated with natural oil for better utilisation. The entire construction (apart from three glulam purlins) is also free of adhesives, glues or varnishes. All connections of the solid wood elements of the ceilings and roofs as well as the wall constructions are therefore screwed. This means that they are easy to dismantle for later conversion or even dismantling and can therefore be recycled in the material cycle.

The wood in the interior is largely natural and only partially leached or oiled when the surfaces are used more intensively. © Patrick Möhrle

The clients wanted a house with a special focus on healthy living and sustainability, which is why unnatural materials were completely avoided in the interior. © Patrick Möhrle

Where the walls are plastered, clay was used, which actively influences the indoor climate. © Patrick Möhrle

Sustainable, healthy materials

The strict principle of sustainability and pure separability is also applied to the building insulation, which consists of chopped straw and soft wood fibres. The straw, which is compressed for use as thermal insulation, offers very good thermal protection, while at the same time its grey energy is significantly lower than that of conventional insulation materials. Straw can also be used without additives and, should the building ever be dismantled, can either be reused or returned to the natural cycle. The interior walls are plastered with clay, of which a total of 50 tonnes are used in the building. The indoor climate is greatly improved by the regulating properties of the clay. The materials used, explains architect Michael Welle, ‘have been transformed from the past into the present, in that they are the same as they were hundreds of years ago, but processed using today's modern manufacturing techniques.’

The pentagonal building is positioned according to the topographical features of the site and responds to the outdoor area statutes and the edge of the road. © Jürgen Pollak, Stuttgart

Building-integrated building services

The client's desire to maintain an interior atmosphere that is as natural and healthy as possible also influenced the building services planning. All three storeys (plus a small attic storey) are heated by a log heating system with an output of 21 kW. As a precaution, the local heating network was also fed into the house for future requirements and can be connected at any time. Additional heat comes from solar collectors on the south-east face of the roof, which is otherwise almost completely covered by an in-roof PV system with an output of 14.5 kWp. A 1000 litre buffer storage tank and a 9.5 kW battery store the energy generated. The envelope of the building is therefore only 4% worse than the KfW 40 standard; in terms of primary energy, it is even 18% better than the KfW 40 standard. The project thus demonstrates how an appropriate combination of traditional materials and modern technology can be used to create healthy living spaces and energy-saving buildings.

The south-east side of the roof is almost completely fitted with a PV system, and there are also four collectors for solar heat generation and two skylights. © Jürgen Pollak, Stuttgart

Orginally written by Thomas Geuder