Building with straw can completely change how we use resources in construction, how we heat and cool our homes, and how we relate to the buildings we inhabit.
Straw bale building has unique and important answers to a few broad questions that help us get to the heart of sustainable building:
• What materials will have the lowest environmental impacts during and after construction?
• What materials and techniques will result in the most effective building—one that is durable, efficient, safe, healthy, and comfortable?
• What materials can be used together to make a building appealing over generations because of its resonant beauty, sense of solid shelter, and peaceful comfort?
The straw in bales is left over from grain harvesting. Crops aren’t grown just to make straw bales: the plants are being grown for rice, wheat, barley, or oats. Once the grain is harvested, the stalks are bundled together into bales.
Straw is an abundant agricultural by-product with few uses, and using straw bales as a building material is a great example of upcycling. Unlike wood, straw is an annual crop and can often be sourced locally—frequently from less than 100 miles from a building site. That results in a small carbon footprint: other than the energy it takes to bale the leftover stalks and then deliver that bale to your job site, all of the other resources needed to produce that bale were used for the production of food.
The California Straw Building Association (CASBA) is currently studying how much carbon a straw bale wall sequesters. Plants draw carbon out of the air as they grow and lock it up, releasing it only when they decompose (or burn, which is what happens to many grain fields when the straw is not upcycled). By keeping the straw in the wall, the carbon is not released into the atmosphere (see “Carbon Sequestration” sidebar).
Plastered straw bales replace the insulation and drywall, and often the paint. They can reduce the amount of lumber needed for framing, and may even be part of the structure. Leftover straw can be used as fiber in the plaster, or used onsite as mulch without further processing. And at the end of a long life in a straw bale building, a straw bale is biodegradable.