Given the recent tragedy of the Victorian bushfires, in which many lives have been lost and at least 1800 homes destroyed, we thought it pretty timely to write about the information available regarding the fire resistance of strawbale walls. The susceptibility of strawbale buildings to fire hazards is a surprisingly common question when talking to the uninitiated, but most people don’t take long to realise that for any material to burn, it needs a good flow of air, and trapping air, not allowing it to flow through the bale, is what the insulative value of strawbales is all about. During the stacking of the straw, large amounts of loose straw accumulates very rapidly, and this loose, dry mass can be extremely flammable, but this period is relatively brief, and a bit of basic housekeeping with a plastic garden rake quickly minimizes the risk. The most recent Australian work we have found available was conducted in 2002. The principle organiser and motivator behind this testing was architect, Bohdan Dorniak, past president of Ausbale (Australasian Straw Bale Building Association). Bohdan is to be commended on his dedication and hard work in getting strawbale established as a widely accepted building material in Australia. The testing we are referring to was conducted by the CSIRO Building, Construction and Engineering division in North Ryde, NSW. (See link to Earth Garden article below) The bales tested were rendered in earthen lime, and cement based renders, and all performed well enough to exceed the required standards. According to Bohdan’s Earth Garden article, the “samples were subjected to a simulated bushfire front with the maximum heat intensity being rated at 29 kilowatts per square metre” (imagine 29 1000 watt heaters all crammed up against one square metre of wall). In the article alone, we aren’t given a time period over which this energy is applied to the wall. Brian Menadue, of the South Australian Country Fire Service was present at the testing and was quoted by Bohdan Dorniak as saying “rendered strawbale would be an acceptable wall material”.
http://www.earthgarden.com.au/strawbale/fire_test.html
Check out this link for information from the Australian Government on strawbale and fire resistance.
http://www.yourhome.gov.au/technical/pubs/fs58.pdf
There are plenty of other aspects to fire proofing your strawbale home which i will cover in coming weeks.
Hooroo
