Strawbale Building is one of those endeavours that mostly flies below the radar. Although a proven construction method for more than 100 years, the mainstream building industry don't really allow it to appear on their screen.That might be because it's been hard to pigeonhole. After all, the raw material is scooped, as agricultural waste, right off a farmers field, instead of shipped out a factory door, complete with specification and safety data sheets. But that distinction might be about the change.
Oryzatech make their Stak Block from compressed rice straw, considered the world's largest bio-waste crop. The interlocking blocks do look uncannily like Lego for giants. Each fire resistant block weighs about 13.5 kg (30 lbs) and contains 96% recycled content, as well as being rated to R50 for insulation*, which is claimed to be thrice that of a standard insulated stud wall.
Testing at California Polytechnic University found that Stak Blocks were not only highly insulative but also seismically strong: "better than wood framing and less brittle than concrete walls," is how Oryzatech put it.
Being a waste agricultural product Oryzatech Stak Blocks are said to sequester carbon dioxide. The company don't go into great detail about their manufacturing operation, but it is described as "a scalable, low energy-production process." However a peek at one of their patent applications hints that straw stalks and an undisclosed binding agent are squished under pressure at temps of about 120 to 175 °C (250 to 350° F).
Elsewhere in the patent application Oryzatech allude to the reasons we cited above for strawbales glacially slow acceptance by the broader industry. "... in 2002 one million straw bales were used for building construction and the majority, if not all, of the straw bales were provided directly by independent farmers. As such, contractors have typically been required to adjust their building practices based upon the fluctuating size and quality of the bales produced by a particular farmer's equipment and baling practices."
Which leads on to this observation: "Accordingly, not only would it be attractive to provide a construction material effectively comprising recycled straw stalks that have little other practical use, but it would be especially desirable to provide such a material that will yield consistent and uniform characteristic."
Aside from the hiccup that Oryzatech's Stak Blocks are still in the developmental phase, and on the look out for new investors, we wonder if they couldn't have engineered out the need to bolt the blocks to a building's foundations with rather copious use of threaded metal rods? Kinda of cancels out all that wonderful carbon sequestration, if you also have to guzzle heaps of energy making steel rod.
But ignoring that caveat, Stak Blocks sound like a great idea, that just might have mainstream construction embracing the many benefits of building with straw.
NB: *(Insulation R ratings in the USA are very different to the rest of the globe. Surprise, surprise. If my maths is correct R50 in the US equates to R8.8 everywhere else.)
Images (from the Top): Jetson Green, Patent Storm and Oryzatech
More Strawbale Building
• Straw, Sticks & Bricks - an EcoMaterials Resource
• Strawjet - A Modern Marvel Top 25 Invention of 2006
• Strawbale Housing in Europe
• Strawbale Police Station for Visalia, California
• Hemp-baled Houses
• Crikey! World's Largest Wildlife Hospital is Made of Strawbale
• Straw Bale Eco House at US Botanic Garden
• Building Green: Energy Efficiency and Aesthetics From The Same Materials (Part 20)