Straw is a by-product of the grain industry (be it wheat, rice, sugarcane, or barley stalks) that can be baled into a relatively tight bale. Compared to mainstream building materials, straw has relatively low environmental footprint and, grown as an annual crop, is very sustainable.
Rendered strawbale walls have a high insulation value known as the R value (which rates the ability to resist heat flow). The higher the R value, the better the insulation. A strawbale construction may typically provide values around R8.0 to R9.0., compared to R2.6 to R3.0 for a standard brick veneer build, although the R value achieved will be dependent upon the compactness of the straw, as very compact bales have a lower R value.
There have been very few problems reported regarding insect or rodent infestation in strawbale buildings. Fully rendered strawbales seal the walls, and the bales themselves provide very little food for pests.
Termites seem to be adverse to straw. It has been observed that termites have entered a strawbale home, left the straw alone and damaged timberwork. However, all homes and buildings of strawbale construction should be protected against termite infestation in accordance with best practice as outlined in the building regulations.
Rendered strawbales had been tested by the CSIRO and results indicated that rendered strawbale walls were suitable for construction in bushfire zones (bushfire attack level 29 – high). However, following recent Bushfires in Victoria and NSW and the introduction of a new test regime with higher specifications, further testing will need to be carried out to determine the suitability of strawbale construction in high risk areas. If you’re considering building a strawbale house in a bushfire zone, please contact for an individual risk assessment.
Moisture is perhaps the biggest problem strawbale homes face. In conventional construction the exterior cladding of a building is generally waterproofed. This is not the case for rendered strawbale walls and the reliance is on “water resistance”. Renders that are “permeable” or breathable will allow water vapour to dry out.
The use of a “toe up” on the floor (a raised base), will help prevent any liquid that may be spilled from “wicking up” into the wall. All walls should be built on a damp proof membrane (similar to a brick wall) to minimise exposure to moisture.