Green Living

[Herb Fellow]

Imagine if we could grow a building material that combined the benefits of having a low density, high thermal insulation and being air-tight? Bowen Islanders Kim Brooks and Jayeson Hendyrsan have set out to prove that hemp can do all of the above, and more.

When the couple bought property on Bowen, they were determined to build an eco-friendly home. They considered a straw-bale structure, but dismissed this option after extensive research showed numerous problems with mold and moisture. When they looked into building a hemp house, they found that no construction manual existed, so Kim and Jayeson developed their own method. They decided to use hemp hurds (a product made of hemp stems) that had been chopped up like wood chips. The chips were soaked in water and lime, then mixed with sand and cement. This mixture yields an organic, light-weight cement that is referred to as hempcrete. Using formwork, Kim and Jayeson molded solid monolithic walls that are supported by a post and beam structure. To minimize the cost as well as the ecological footprint, salvaged wood was used where possible.

“The building would be much more economical if we didn’t have to use a post and beam structure,” Kim admits, “but we didn’t know if the walls would be weight-bearing.”

They do know that the integral 12” walls make sound and thermal insulation virtually unnecessary. Kim and Jayeson’s dwelling stayed warm during the past winter, even during lengthy power outages. And the sound of howling winds was shut out completely when they closed the doors. Hemp building advocates believe that hempcrete walls are up to seven times stronger than those made of concrete, half as light and three times as elastic making them more resistant to stress-induced cracking and breaking. This makes hemp buildings suitable for earth-quake prone areas. Hempcrete is also resistant to rotting, rodents and insects; it is fireproof and waterproof.

Building their home has been a family effort for Kim, Jayeson and Sashie, their 13-year-old daughter. Jayeson took on the roles of contractor, builder and construction manager; he handled research as well as heavy labour. Kim was responsible for the architectural design and property development. She ensured that no toxic substances were used, even inside the house. Sashie has made hempcrete the theme of her science fair project at Island Pacific School, where she attends grade eight. She has studied its thermo conductivity and thermo mass. Wielding a blow-torch, she also set out to test the fire resistance of the material. A charred, but intact hempcrete brick is the result and Jayeson is thinking of adapting this method for getting rid of pockets of mold left over from the winter in the yet untreated walls.

The challenges in building with hemp mostly came from trying to meet industry standards. To obtain a permit, Kim and Jayeson had to provide extensive documentation including lab results. “The building inspector basically said: ‘What kind of questions should I ask you?’” Kim recalls. “We initiated many of the lab tests ourselves, because we wanted the house to conform to the building code. How do you know that you have enough insulation if you don’t use ‘insulation’?”

Building the house is Kim and Jayeson’s first step toward sustainable living. They plan to publicize their method of hempcrete construction, teach interested individuals or groups and maybe write a book about the process.

Source: Bowen Island Undercurrent
Copyright: 2008, Bowen Island Undercurrent
Contact: Susanne Martin - Bowen Island Undercurrent
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