Sunday, January 24, 2016

CONSTRUCTION CORNER: Biomaterials for better building

By Korky Koroluk

By mixing old-fashioned building materials — straw, clay, wheat, grasses and the like — with innovative binders, researchers in Europe are hoping to develop materials with lower embodied energy and improved energy efficiency.
CONSTRUCTION CORNER: Biomaterials for better building
They hope, too, that these materials will mean greater comfort for building occupants than is sometimes the case with conventional building materials.
A long-term research project dealing with biomaterials has just been launched with funding from the European Union. Dubbed ISOBIO, it's one of many aimed at providing the architecture-engineering-construction sector with tools better suited for meeting today's imperative of reducing emissions of greenhouse gases in the hope of limiting global warming.
But the researchers are well aware that any innovative materials must meet a number of criteria.
"We hope to develop materials that are competitive in every sense," says Alan Taylor, project co-ordinator of the new program. "We want to solve the 'trilemma' of guaranteeing the security of supply of materials, producing materials that have a genuine competitive edge and reducing emissions."
Taylor is with TWI Ltd., a British-based engineering consultancy.
The new program has begun by identifying promising organic materials that could be used as insulation, many presently classified as waste. Finely chopped bio-materials such as hemp and straw are being treated with special resins and nanoparticle gels so that they become robust, resistant to moisture and fire retardant.
Researchers are looking at combining organic and inorganic materials. The inorganic materials might have excellent insulating properties, for example, while combining them with inorganic material could make the end product more robust.
It's not as easy as it sounds. Consider hemp. When it is combined with a lime mortar, there is a chemical incompatibility which may result in a reduction in the strength of the composite material. It's in cases like that where nanotechnology comes into play.
Nanotechnology can best be described as the science of the extremely small. Scientists have discovered that engineering materials at the atomic or molecular scale can result in surprising — and very useful — results. So when we're talking about nanometres, we're talking a billionth of a metre. An average human hair, for example, is about 80,000 to 100,000 nanometres across.
Because of the nano-engineering involved, it may turn out to be possible to add hemp to mortar. So the new bio-aggregates can not only improve the performance of conventional materials, they can also offer new features.
Speaking of hemp, the shiv, which is the core of the hemp stalk, has a porous structure that provides moisture buffering, which helps maintain humidity inside a building at a more constant level. But to achieve that property, the shiv must be treated with hydrophobic resins. The result is that water vapour can travel in and out of the material, but liquid water can't penetrate it.
"We're striving to find the delicate balance between applying the right level of coating on the hemp shiv and preserving...its inherent properties, such as porosity," Taylor says.
He adds that any new biomaterials developed must not only be technically feasible but commercially viable as well. So the key question becomes:
"How do we adapt the materials to the existing manufacturing processes for conventional materials?"
So ISOBIO, during a later phase of the project, will be manufacturing biomaterials and conducting tests on a series of industrial-scale demonstration prototypes.
ISOBIO is also doing Life-Cycle Assessments of a wide range of materials both old and new. Such assessments are often referred to cradle-to-cradle analyses, and have become essential for making "green" decisions. They aren't really about distinguishing good products from bad products; they are mostly about informed decision-making.
"A purchasing manager may not consider operating cost, ignore the thermal performance of a building or the embodied energy used to construct it," Taylor says.
"We need to move away from 'this is the cheapest' to consider whole-life cost."
Korky Koroluk is an Ottawa-based freelance writer. Send comments to

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