‘World First’ for Bale House inwales
In what is believed to be a world first, a bale house is being built in north Wales using miscanthus, a carbon-negative renewable energy crop.
Following successful test building last year, the University of Aberystwyth, the Centre for Alternative Technology (CAT) and commercial partner Terravesta are working on building a miscanthus bale house with an expected lifespan of 100 years.
Miscanthus is a perennial crop with excellent insulation value that is grown on low-grade marginal UK land. The miscanthus bales are being used as in-fill for a timber frame, in the same way as wheat straw bales are often used, with the surface of the bales providing a ready key for internal clay plaster and external render.
“The most groundbreaking thing about miscanthus is that it could decarbonise the construction industry at scale,” says Bee Rowan, straw bale building course leader at CAT.
“In conventional building, the carbon footprint is heavy and one house can emit 50 tonnes of carbon dioxide. In contrast, approximately 40% of miscanthus biomass is made up of carbon directly captured from the atmosphere in photosynthesis. Locking this carbon up in building materials actually reduces atmospheric levels of CO .”
2 The building (CENTRE) uses ‘ two-string bales’ supplied by miscanthus supplier Terravesta. These are just over a metre long, 450mm wide and 350mm high, making them a convenient building block size that can be handled easily.
As part of the project, plant breeding scientists at the Beacon Project at Aberystwyth University are developing seed-based miscanthus hybrids that work well in straw bale building. “Miscanthus is currently grown from rhizome — it’s planted once and harvested every spring for 20-plus years,” says Dr Judith Thornton.
“Our scientists have developed miscanthus hybrids that can be grown from seed to suit particular markets. These have typically been the biomass and bioplastics markets, but by matching up our understanding of the plant properties with the requirements of the building industry, we can potentially breed for the house building market,” she adds.
This will open up a lot of opportunities for self-builders, believes Dr Thornton. “While building directly with bales is ideal for self-build housing, in the future we could be using prefabricated panels of miscanthus to build houses, and we could also produce loft insulation or fibreboards.”