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Protecting against fires has long been important to code officials, builders and homeowners alike. None of us want to see our homes go up in flames or experience the loss and grief associated with fire. Building codes exist to protect homeowners from fires, both minor and catastrophic. Even with those codes in place, we have seen that a well-built house can burn to the ground in a matter of minutes. To me, the reason for this is obvious. A conventional stick-framed home is nothing more than a series of chimneys behind a thin layer of fire protection. What many homeowners don’t know is that the majority of the fire protection required by code in a conventional home is in the form of drywall. That’s it! 1/2″ of gypsum board is all that is required to protect you from fire. Once that drywall barrier has been compromised, there is nothing to stop the fire from attacking the structural wood and/or steel framing in your home.
Straw bale homes are different. Straw bale houses are known for their fire resistance and have been independently tested showing that they resist fire by up to three times that of conventional homes. Three times the protection may be the difference between a total loss and a house that can be saved. In a straw bale house, the first line of defense is the application of 1 1/4" of plaster. The plaster provides far superior resistance to flame than most sidings.
The second, and often most surprising element of straw bales that increases the fire resistance is the bales themselves. When most people think about straw and how it performs in fire, they think about barn fires, spontaneous combustion, and other fire stories. The fact of the matter is that barn fires are caused by hay that was baled too early and thus has high levels of moisture still in the crop. The fires start when that moisture creates heat by decomposing the hay. The hay then flares from the heat of the decomposition process inside the bale.
Straw is baled when the crop is dead and dry, usually around 8% moisture content by volume, so no interior decomposition occurs. Moreover, the bales are so tight that there just isn't a lot of space for oxygen to easily move through. Fire cannot exist without oxygen, so once again the bales have created a form of protection against flame spread. Consider that a bale is like a phone book. If you rip out the pages one by one and light them on fire, they will burn: so will loose straw (although not very well, due to the high silica content). If you hold a lighter under the entire phone book, however, you will likely run out of fuel in the lighter before the book catches fire because there is no oxygen in between the pages to support the flame. The same is true for the baled straw.
Put the two systems together: thick plaster on both sides of the wall and dense, oxygen-deprived bales inside and you get a combination that makes for a very fire-resistant wall. Protecting your home from fire in other ways is still important. Be sure to clear brush from around your house, clean out your gutters and under your decks, and so on. There are several sites that offer guidance on how to protect yourself from wildfires, and I strongly recommend you visit them.
My wish is for people who live in fire-prone areas to start getting serious about protecting themselves from fire. Tens of thousands of homes and buildings have been destroyed in the last several years. Most of the people who lost their homes will rebuild. I[ah2] invite them to build with bales instead of building another conventional home. The benefits go beyond fire protection and reach into the world of green construction and healthy homes.