Straw bale building was invented in the 19th Century by settlers in the plains of Nebraska. They needed an alternative building material where timber was scarce, and ended up with a natural builder’s dream.
Straw bale building uses a sustainable resource to quickly build breathable, super-insulated structures which require little or no non-solar energy to heat if designed right. Straw bale buildings are naturally soft-edged and pleasing to the eye and lend themselves to flowing curves and smooth lines.
Straw has very firm credentials as a sustainable material. Firstly, straw sequesters more carbon in itself than the carbon expended in its cultivation and transport. It’s super-insulative properties also help to reduce carbon emissions throughout the lifecycle of a building. Buildings whose walls are built from straw bales are extremely snug; they provide much more insulation than is required under the building regulations (if you’re interested: a typical 450mm thick bale has a u-value of 0.13W/m2K).
Like earth, straw is a healthy, breathable material and functions in tandem with breathable plasters and renders. A straw bale home with breathable plaster and render will self-regulate its humidity levels to provide a healthy, pleasant living environment free from dampness and condensation.
Straw is also (surprisingly) durable. Many of the buildings from the Nebraska settlers’ first attempts are now more than 100 years old, and still standing firm. So, as yet, the upper limit for straw bale durability has not been established.
Straw functions well as a load-bearing material in most domestic contexts. It can easily be used as a load-bearing element in a two storey house. However, if you want to go much beyond this then it’s possible that straw will no longer function as a load-bearer. In this case, you need a structural frame built of a material such as wood, and the bales then function as infill.
However – there’s little point in super-insulating your walls unless you do the same with your roof. Straw bales or compressed strawboard can be used as a roof or wall insulation.
