Straw house withstands 120mph winds

The Balehaus at Bath was built by industrial partners Modcell as part of a major research project to scientifically assess the performance of straw as a sustainable building material. The two-storey building was officially opened by Grand Designs presenter Kevin McCloud last year.

The research team, led by Prof Pete Walker, director of the university’s BRE Centre for Innovative Construction Materials, has been monitoring the house since October 2009 for thermal performance and humidity levels, and has now tested the structure of the house for resisting winds up to 120mph.

The wind load was simulated using hydraulic jacks that pushed horizontally against the walls with a total force exceeding four tonnes - equivalent to the dynamic force of a hurricane. During the tests, the walls moved no more than 4mm under peak loads - well within design requirements and as predicted.

The researchers will use these data to develop a theoretical computer model of the house to simulate how a three-storey, or even higher, Balehaus building would withstand such winds.

The research team, including Dan Maskell and Dr Katharine Beadle, had previously conducted similar tests for racking strength on the individual wall panels. This, however, is the first time a whole house made of straw-bale panels has been tested in this way.

Prof Pete Walker said: ’The recent test result is excellent as it has both confirmed the robustness of Balehaus and validated the computer model, so avoiding the need for further tests and providing a basis for safe and efficient structural design.

’We hope the data we’re collecting on the Balehaus will help strengthen the case for the mainstream building industry switching to using more sustainable building materials such as straw.’

The Modcell Balehaus system consists of prefabricated panels infilled with straw bales. Due to the high insulating properties of the panels, the Balehaus minimises additional heating requirements and could reduce heating bills in housing by up to 85 per cent, and CO₂ emissions by 60 per cent.

The research work on Balehaus involves eight industrial partners and has been funded by the Technology Strategy Board and Carbon Connections.