Efficient walls made of agricultural waste
Straw buildings are nothing new, but sometimes revisiting old solutions can provide useful options. In this article on building efficient walls with agricultural waste, ArchDaily gives us a nice overview of such a look back and shows how “straw buildings can be sustainable, comfortable, and, above all, solid and resistant.”
The stems [of leftover wheat, rice or barley] can be compacted into rectangular bales, which can be stacked and used as fillers or even as self-supporting walls in a technique known as the “Nebraska” style, widely used in the 19th century on the plains of this US state. While field bales can support around 900 kg per linear meter, high density blocks of the same material, compacted by machines, are designed to support up to almost 6000 kg / m.
That being said, straw is most often used for sealing or insulation purposes in combination with more common structural materials like wood or steel.
Because it is a material formed mainly of air, straw provides excellent thermal insulation in construction. It is estimated that a well-built straw bale house can save almost 75% in heating and cooling costs.
Since two significant problems related to building straw bale walls are moisture and mold, the foundations must be raised at least 20cm above ground, and eaves must be relatively large to keep the walls well protected.
Being 100% biodegradable, when straw buildings become obsolete and need to be demolished, its walls can decompose into the soil without major problems. But like any building material, it will only be truly sustainable if it is available locally.
Which is one of the conclusions various projects exploring sustainability regularly come back to; sustainable often equals local. Concepts and materials that look “green” only prove to be so when their other impacts (like transport) are factored in.
Image: Ecologic Pavilion In Alsace / Studio 1984. Image Cortesia de Studio 1984.