Straw is cheap, low carbon, good for the environment and an excellent insulator.
So why don’t we see more straw houses, especially since excess straw in the UK could build a new city each year?
For the past ten years the University of Bath has conducted R&D on the use of straw bales. Starting with straw as a low-carbon cladding solution, this moved to developing panels that could bear heavy loads and then low-energy prefabricated straw bale houses.
Panels have been subjected to fire tests, thermal transmittance tests, accelerated weathering tests, acoustic tests, simulated flooding and impact testing and to the “big bad wolf” test: of simulated hurricane force winds. Both panels and prototype BaleHaus have now been granted certification, meaning that insurers will cover straw houses and home-buyers will be able to obtain mortgages.
Reducing Energy Consumption
Since the UK construction sector must reduce its energy consumption by 50% and its carbon emissions by 80% by 2050, radical changes are needed to the way we approach building houses.
- The manufacture of cement, used in concrete, is responsible alone for up to 8% of all industrially produced greenhouse gas emissions.
- Traditionally, the environmental impact of construction materials has been significantly less than the impact of occupation (heating, cooling and so on) over the lifespan of the building.
- In modern energy efficient buildings the proportion attributable to that “embodied” in the fabric of the building is expected to increase to at least 90%.
- Measures to reduce the impact of the embodied energy and carbon will deliver even more environmentally friendly buildings.
- On average a three-bedroom house needs 7.2 tonnes of straw
- Straw is low-cost material and, more importantly, as a plant it captures and stores atmospheric carbon dioxide during photosynthesis. Using more and more straw in buildings creates a natural carbon storage bank.
Concerns about straw’s poor durability, fire resistance, attraction for mice and rats and lack of structural integrity, mean it has never caught on as an alternative to bricks, concrete or timber. However, the development of prefabricated wall panels using straw bale for insulation has now provided the opportunity to market straw to the mainstream construction industry. Prefabrication, or off-site manufacture, means that wall panels can be made to a very high specification in a factory, protected from variable weather conditions that would otherwise inhibit on-site building with straw.
BRE’s recent research at the University of Bath has shown that straw bale buildings can reduce energy bills by 90% compared to conventional housing stock.
Similar prefabricated systems using straw bale construction have been developed in Australia, Belgium and Canada. Entire communities, towns or even cities built from straw bales.
University of Bath Research
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