Innovative: ecological lightweight construction

“A light wooden lattice-work construction, straw bales, clay and wooden tiles – and the house of the future is finished,” enthuses supervisor Andreas Trummer from the Institute of Structural Design at TU Graz. He is explaining the apparently simple concept of the arched construction system “strawboid” developed by architecture students Max Schade and Fritz Walter in the framework of their master’s thesis – supported by the Austrian Research Promotion Agency, the land and forestry college Alt-Grottenhof and proHolz Steiermark. How the implementation of good design and clever engineering can be united in an ecologically sustainable and aesthetically surprising result has been revealed at the presentation of the prototype at two events. On 25 September at the opening of the Adventure Day at Stübing Open-Air Museum, and on 28 September at the project presentation together with proHolz Steiermark, also at the open-air museum.

Lightweight construction made of wooden struts

Max Schade’s and Fritz Walter’s master’s thesis started with the idea of testing a lightweight construction system and demonstrating its potential. Lattice-work shells are the most efficient known structures, sometimes even lighter than the air which they traverse. Without technical aids, the design is so demanding that only a few prestige structures have been built, such as the multihall by Otto Frei in Mannheim. But this did not deter Andreas Trummer and institute head Stefan Peters, Dean of the Faculty of Architecture at TU Graz. They counted on the fact that the use of digital aids from the draft to the finished product would open up new potential for innovative construction methods.

From “strawboid” to construction system

The result of this was the strawboid prototype, which was able to be ideally set up at the Austrian open-air museum at Stübing. Erected using wooden slats and straw in a sandwich construction, the structure has the building geometry of a saddle surface. Two wooden lattice-work shells run one above the other, and the intermediate space is filled with bales of straw. A sophisticated bentwood technology ensures that the desired curvature is achieved. Heated up and dampened by steam, beech wood, which is particularly suitable for this technique, becomes soft and pliable. And when cold, it has a stable shape and can bear loads. From experiences with build-it-yourself kits using precise plans, mechanical tests and calculations, a free-form design made of emission-free materials can be derived for other structures.

90% energy savings – zero pollutants

The ecological assessment of the strawboid is remarkable. Compared to a traditional construction made of wooden profiles, the wooden lattice-work construction saves about half of the building material and compared to massive constructions, consumes up to 90% less manufacturing energy. The building including insulation is plastic and pollutant free and can be completely recycled after use.

Sought-after approach

Straw as an ecologically high-quality insulation material is not new. Since the straw baling press was invented 150 years ago, the material has been used as a renewable insulating material and ensures home comfort. Plastered with clay, the bales are protected against fire and pests and are an ideal regulator of heat and humidity. The advantages of straw bale construction were obvious for Max Schade und Fritz Walter because the bales can be easily worked and are perfectly suitable for curved designs. The insulating material rounds off the resource-saving and sustainable approach of the arched construction system. It’s no wonder that people are already interested in wanting to use the still pending “strawboid” concept for ecological apartments or exhibition rooms using thermally sealed glass facades.

The prototype at Stübing is presented with a photoblog.