Derek Olson
Three Ingredients Asheville's "Push House" is built with Hemcret…
Have proponents of the tight building envelope got it all wrong? Anthony Brenner and David Mosrie of Asheville, N.C.–based Push Design think so. Their reasoning is that while builders can specify non–off-gassing materials, they can’t control the durable goods (furniture and the like) that homeowners bring in, which may be loaded with chemicals. An air-tight house that uses less energy may do so at the expense of human health, if it has the negative side-effect of trapping harmful toxins inside. Better to build a home that breathes.
The firm’s prototypical “Push House” offers just such an example. Its stucco-like exterior walls are actually made of 12-inch-thick Hemcrete, a biocomposite masonry compound that’s mold-resistant, bug-proof, and recyclable. And get this: Hemcrete sequesters carbon and other “nasty stuff” from the atmosphere and undergoes a natural petrification process as air filters through it, becoming stronger over time.
Cardboard, Too
Hemp isn’t the only unconventional material making a statement in the Push House. The interior walls look like drywall, but they’re actually an engineered core panel material made of 100% recycled paper and skinned in magnesium oxide. Waterproof, toxin-free, and resistant to mold, fire, and termites, Purepanel has a crush strength of 20,000 pounds per square foot, yet it’s light as a feather. Each of the interior doors in the Push House (measuring 3×8 feet) is made of the stuff and weighs 12 pounds.
$133
Cost per square foot to build the nation’s first Hemcrete house outside Asheville, N.C.
700
Number of years the average Hemcrete building is expected to last
2,500
Pounds of industrial hemp needed to produce the same amount of THC found in one marijuana cigarette
12
Number of weeks it takes to grow enough industrial hemp on 1.5 acres to build a 1,500-square-foot house
60%
Reduction former Asheville Mayor Russ Martin saw in his homeowner’s insurance after moving into the Push House
2.5
Number of weeks it took to build the shell of this 3,400-square-foot home
Hemcrete’s virtues are well-known in Europe, where it is used for everything from walls to roof insulation, but the Push House marks its first residential foray on this side of the Atlantic. Brenner estimates the cost of each exterior wall at $25 to $30 per cubic foot, but that’s partly because some raw materials had to be imported from the U.K. Domestic production could cut the price tag in half, he says, except for one problem. It’s illegal in the U.S. to grow Hemcrete’s primary ingredient—industrial hemp—which is derived from the stalk of the cannabis plant.
“Right now you can import it but you can’t grow it,” he says. “There’s a stigma that marijuana and industrial hemp are the same thing, but the THC content of industrial hemp is actually only .035 percent.”
Although builder interest in the material is as yet undetermined, there’s no shortage of cash-strapped farmers interested in growing the rapidly renewable plant. In fact, 11 states have approved its cultivation under state law. But the U.S. Drug Enforcement Agency has so far nipped all such enterprises in the bud.
Learn more about markets featured in this article: Asheville, NC.
