Are straw bales the future of sustainable building?
As designers and homeowners look for imaginative ways to help reduce their carbon footprint in the campaign against climate change, straw bale could become a new tool in the building industry's armoury. Straw, a natural by-product of farming, is collected and baled, tightly compacted, and fitted into a frame before being rendered with earthen or lime stucco. The practice was prevalent during the 1800s throughout the American prairie states but fell out of favour with people turning to bricks and mortar. Unlike hay, straw contains no nutritional value for livestock and is often sold as bedding for farm animals — or burnt. Unlike other recycled materials currently used in the building industry, such as car tyres or recycled plastics, straw bale can be used in its raw state requiring no further processing.
The crops that leave the husks that are turned to straw trapped carbon during its growth cycle, and because straw bale can often be sourced locally, its use in buildings is often carbon-neutral and can even be carbon-negative. Once the building is no lo longer required the straw bale can be broken up and will naturally biodegrade. So why aren't more of us using it? The Maya Guesthouse, situated in the village of Nax in the Swiss Valais, will be the first hotel in Europe to be built entirely from straw bale. Not only are the walls a carbon sink; once complete, the building will require almost no heating, except in the extremes of an Alpine winter. 'Having straw bale walls means taking hundreds of tons of CO2 from the atmosphere and stocking it for hundreds of years inside the walls,' notes owner, Luis Papadpoulos. 'Authorities are more and more open to new building methods. An administration building in Lausanne was constructed with straw bales last year. Straw bale homes can be affordable for many, especially if you wants to build it yourself.'
All this sounds very exciting and the idea of using waste products to build badly needed affordable, carbon neutral housing could be the perfect solution to the UK's housing crisis. But no building method is perfect and in the case of straw bales, the big question is: just how safe are they? Building a house from dried straw sounds like a fire hazard waiting to happen, especially with the electrical wires that crisscross every modern home. Despite common sense objections, straw bale has proven itself a very resilient building material passing stringent fire tests around the world. The Commonwealth Scientific and Industrial Research Organisation in Australia tested the product thoroughly before declaring it safe for use even in areas prone to bushfires. Once tightly compressed and rendered, straw loses the susceptibility to ignite of a single piece of loose straw, much in the same way a telephone directory is harder to set alight than a single piece of paper.
Bath University recently built the BaleHaus and has been subjecting it to various tests to clarify its safely. The two-storey structure, built from straw bales and hemp panelling, underwent a fire test in 2009. The building was subjected to 1000°C temperatures for two hours, four times longer than the legal requirement and still did ignite. The university has also been running wind tests. Using hydraulic jacks, researchers imposed four tonnes of pressure onto BaleHaus, producing a force equivalent to that of a hurricane. The resulting four millimetre shift was well within safety recommendations and the team are now looking to try and test a three-storey building in the near future.
Article continues at ENN affiliate, Ecologist
Bales of Hay image via Shutterstock