Straw—the dried stems of grasses, reeds and other plants—is used worldwide in traditional building, especially in thatched roofs, like this one from Polynesia. Straw, like wood, stores carbon from the atmosphere in the building envelope and thus contributes to making carbon-neutral buildings.
As a waste product of cereal production, straw is often burnt, tilled into the soil, or simply left to rot in the fields. So its use in building can lead to both ecological and economic advantages.
Straw is light in weight and has high insulation value; thus, a thatched roof provides the building with both waterproofing and insulation. Thatching is still widely used for roofing around the world, but can be expensive due to the skilled labour and high-quality materials required.
In the late 19th century, the invention of the baling machine led to new applications of straw in building. In the Great Plains of North America, especially in Nebraska, where timber was scarce, straw bales were stacked like bricks to make highly insulating, load-bearing walls for houses.
Starting in the 1990s, there was a resurgence in straw bale construction as a way of building low-cost, environmentally friendly, highly insulated housing. Both Nebraska style (load-bearing) and timber-framed straw bale houses, many of them self-built by the owners, have proliferated around the world. Provided care is taken to protect the bales from moisture, straw bale houses can be both durable and very comfortable.
Another application of straw in building is in prefabricated panels. Straw can be compressed in a mould at 200 degrees Centigrade and will keep its shape when it cools, with no need for adhesive. This process was invented in Sweden in the 1930s and the panels have since been used in a wide range of applications.
Nowadays, straw is being prefabricated into wooden-framed Structural Insulated Panels which can be joined together quickly on the building site. These panels provide an easy alternative to more labour-intensive methods of building with straw.
