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Compostable walls: Straw-bale house in Dornbirn
Ecological and inexpensive – these two criteria are not always easy to reconcile with exacting architectural demands. In the planning for a residential building in Dornbirn, Austria, Georg Bechter Architecture has come up with a convincing solution that does not compromise on design, namely by using straw walls for insulation and as a load-bearing structure.
Architect: Georg Bechter Architektur + Design, Langenegg, Austria
Location: Dornbirn, Austria
At first glance it is hard to tell that the idyllic building – with its exterior lime plaster finish and interior clay rendering – incorporates straw as its basic material. Simply the surface texture of the outside stands out in contrast to the immaculately machined wood elements of the roof and façade, lending the building a touch of natural charm. According to the architects the whole wall structure is compostable. While walls in this form and of a comparable thickness would be barely conceivable in inner city areas, here they not only create a cosy atmosphere through incorporation of niches but also fulfil necessary insulation requirements. The wooden roof structure is also insulated with straw.
This particular choice of material offers the additional advantages of being rapidly renewable and low in cost, and moreover does not require treating. The upward-angled canopy roof shelters and frames terrace areas that are to provide shade in summer and enable ample solar radiation in winter. Indoors a screed floor conjoined with the floor slab serves as a natural heat reservoir, whereby a simple tiled stove acts as the sole source of heating.
The interior of the house is characterised by an open room concept, with the ground plan featuring four wooden cubes and room-high sliding elements for a flexible and individual division of space. The 1.20-metre-thick outer walls made of stacked straw bales not only form the facade of the single-storey building without any need for a wooden structure but in the area of the wall openings enable cosy niches for passing the time and relaxing.
Harmoniously matched building materials create a consistent look both indoors and out. The overall height of the roof and its shape were chosen to ensure ideal exposure to light and heat according to the time of year. Moreover, the deep reveal of the roof forms a pleasant design counterpart to the "naturally formed" straw walls. Although the core material – straw – is not visible as such, it pervades the atmosphere of the house and is not only inexpensive but also sustainable.
Structural engineer: Eric Leitner, Schröcken, Austria