Three Shades of Green

The Simma House, located in Egg, Austria and designed by the architect George Bechter, marries three approaches to sustainable design: the adaptive reuse of an existing structure, the nearly exclusive use of renewable resources in the new construction, and the adoption of German passive house strategies to dramatically reduce energy consumption. The original masonry house which was built in 1966, is typical of post-war residential architecture of the region, particularly in its relatively shallow second story space housed within the peak of the roof and it’s limited use of insulation. Rather than demolish the existing structure, the first story masonry walls were salvaged, and a taller second story was added using fairly standard stick frame construction.

In order to address the poor energy performance of the existing building while simultaneously making a statement on what constitutes an ecological material strategy, the decision was made to use straw bale insulation as the driving force in the formal resolution of the project. Both the existing masonry walls and the new second-story stud cavity walls were wrapped in a thick layer of straw bale insulation ranging from 14 to 30 inches in depth, capped on either end by wood sheathing. The straw insulation strategy was expended to the roof, where 30″ deep rafter-boxes were pre-fabricated in a warehouse and craned into place atop the stud-walls. Due to the exceptionally thick wall and roof sections, steeply angled reveals were used around the window openings and skylights to let in as much daylight as possible.

In addition to the use of the locally abundant straw for insulation, local timber was harvested by the owner himself for use on all of the building’s interior and exterior walls, flooring, and window frames. The precise building craftsmanship resulted in a relatively air-tight house which is heated entirely by a small stove in the living room. A controlled ventilation system together with a heat-exchange and an air intake connected to a ground loop result in an energy-conserving house that requires only a handful of heating days in the winter and no mechanical air-conditioning in the summer. If one day the functional life of this building comes to an end, nearly all of it’s materials are untreated and can be returned to the earth as nutrients for the next cycle of growth.

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