It was seventeen years ago that Kim Brooks and her husband purchased land on Bowen Island, located twelve miles northwest of Vancouver, British Columbia and a short commute by ferry from Horseshoe Bay. Kim, who is involved in the high-tech sector, had a history of lung problems and wanted to build a natural home suitable to the climate…
She and her husband Jayeson Hendyrsan started researching options and were unable to find an appropriate solution for their particular needs. Hempcrete Natural Building Limited was established by the couple on Bowen Island in 2001.
After some intensive research, the couple discovered that industrial hemp decomposes very slowly so that any cementitious composite containing this material has time to cure without the concern of outgassing or cracking sometimes found in other natural building approaches. The couple decided that using hemp and a hydrated lime binder to create a bio-composite of hempcrete as a building material was the ideal option.
They experimented with some mixtures, and with a local industrial laboratory, invented the substance they use today for small home construction. They later discovered that a similar mixture has been used for hundreds of years in Europe, “although we don’t know exactly what their recipe is,” Chief Executive Officer Kim adds.
Kim says that their invented mixture, or ‘recipe’ as she refers to it, is somewhat similar to the mixture used in ancient Rome to build landmarks such as the Coliseum but, “adjusted to add the industrial lightweight hemp fibre. That’s really the innovation in it.” Hempcrete walls, like those of ancient Rome, are calcified rock – incredibly durable, yet harmless to the environment.
Industrial hemp has been used for thousands of years to make such materials as rope, paper and textiles. As a sustainable, environmentally-friendly construction material, the industrial hemp used to create hempcrete has been used for decades as a non-weight bearing infill for insulation and thermal mass in homes and high-rises throughout the United Kingdom, France, Belgium, Switzerland, Australia and New Zealand.
In the United States, building with hempcrete is not illegal, although industrial hemp cultivation is because of its perceived relationship to cannabis. Although hemp and marijuana are derived from the same plant species, hemp is marijuana’s tetrahydrocannabinol (THC) deficient cousin (less than one percent THC) and genetically different.
Hempcrete is quite popular in the United States. The import of hemp products to the nation is valued at approximately $500 million annually according to the U.S. Hemp Industry Association. However, it is expensive to ship the hemp fibre from Canada. When growing hemp becomes legalized in the U.S., building with hempcrete will be made more affordable.
Industrial hemp has been grown legally in Canada for almost twenty years by licensed growers who use seeds certified as low in THC. In 2014, the Canadian Hemp Trade Alliance put crop production at about one hundred thousand acres, with approximately one-quarter of that acreage coming from Alberta. The alliance also notes that it is one of the most profitable crops for farmers, averaging returns of about $700 per acre.
Building codes in Canada do not specifically lay out regulations for hempcrete. “I don’t think that there are any building codes that speak to hempcrete specifically. Perhaps that will come at some point. What they do speak to are things like R factors and durability. They’re more concerned about strength and safety.”
So what is hempcrete exactly? Hempcrete is essentially a combination of the hemp shivs – the shredded woody core of hemp stalks – a lime based binder and water. The lime binder adheres to the hemp shivs creating a firm, non-structural building material that can be poured or sprayed into a traditional wooden frame.
Although there is specialty equipment for spraying, “we find it’s just as easy to pour it,” shares Kim. The ratios of the composites are essential. If the ratios are inconsistent, “it may not set up properly. Cost efficiency is also a factor; having the correct mix for the particular application and climate is critical.” She notes that is has taken the company, “years and years of experimentation to get just the right recipe. In different climates, we adjust it certain ways and make the walls thicker or thinner according to what the needs of our clients are.”
Hempcrete is very easy to work with, is lightweight (about 1/7 the weight of concrete by volume) and provides excellent insulation, sound proofing, thermal mass for temperature regulation. It is also an ideal controller of humidity due to its permeability and breathability. It can be tamped into the forms of a load-bearing stud wall and be used on floors and ceilings. Hempcrete tends to be more flexible than concrete and generally cures in a few hours.
Compared to a traditional wall system, “our wall is an integral monolithic structure,” explains Kim. “There’s nothing in it except the poured material. There’s no added insulation or vapour barrier. It’s just a thermal mass wall system.” Hempcrete is hygroscopic so the walls are ‘breathable’, meaning they have the ability to soak up moisture and then release it. This avoids a situation where water vapour is retained in the wall. There are no mould, mildew or other water-related issues.
Hempcrete is also toxic to pests including rats, carpenter ants, termites and other crawling insects because of its lime component, “So we don’t have any of these infestations and related issues,” explains Kim.
In terms of maintenance, Kim notes that her home’s walls haven’t required painting in sixteen years. The walls are plastered with ‘Stonehemp’ the company’s specialty plaster comprised of a lime wash, water, a bit of sand and ground hemp. “The pigments are embedded in to the plaster which is also a hempcrete plaster. It’s a single structure basically.”
Wall colours are minerals mined from the earth that are used in such items as pottery. “They’re absolutely natural materials – nontoxic. We don’t use any petrochemical based paints at all. It’s all natural pigments.”
The cost to build a home with hempcrete compared to a build using traditional methods will be similar, but the benefits far outweigh traditional builds. “If you’re in construction, you know that much of the costs are really in the finishing details,” says Kim. “I would say that building these homes, as we’re doing it now, is not going to be necessarily any cheaper at the outset. However, the value of it is that our homes are very, very durable. They’re not built to just last a decade or two. They’re built to last forever, and they’re low maintenance.”
As noted, one of the benefits of hempcrete construction is its thermal wall mass properties. The bio-composite material stores energy quickly and releases such energy in response to a room’s fluctuations in temperatures. A room will be cool in the summer and warm in the winter resulting in more comfortable living conditions.
“It’s a passive system. When the thermal mass heats up, it stores the heat very nicely. And the quality of the heat is just different. There’s no dry air blowing around. I think that makes for a really lovely experience, actually, being in the home. That’s just from my own personal perspective … It’s also exceptionally quiet.”
There’s no doubt that their cost-efficient, environmentally-friendly hempcrete home on Bowen Island is Kim’s own little piece of paradise. “I just can’t find any flaws with it,” she says. “I have no more lung problems. We’ve found something marvellous and we want the world to know about it.”