Rooftop revolution 

Turf-topped houses take root in the Garden City

Three stories above North First Street, atop Missoula’s Gold Dust Apartments, corn, raspberries and garlic sprout from rectangular garden beds made of corrugated steel. The living roof, as it’s called, offers a sweeping view of the Missoula Valley and the opportunity for Gold Dust residents to grow their own food in a distinctly urban environment.

“We get a lot of tomatoes, sunflowers,” says building manager, Matthew Reed, motioning his hand to the east.

In addition to providing a natural refuge for Gold Dust residents, the garden also absorbs stormwater, buffers noise and insulates the building, helping keep it cool during western Montana’s warmest months.

“It’s very low maintenance,” Reed says. “The idea is, it’s an organic system.”

This garden marks a local revival of a trend that, though relatively uncommon today, was a frequent feature during ancient times. As early as 1250 BC, northern Europeans lived in turf-topped houses. Nordic migrants arriving from places such as Scandinavia and Iceland in the ninth century brought the technique with them. They used timber and stone to construct buildings, and harvested grass and sod to insulate exterior roofs and walls.

  • photo courtesy Studio Modera

The practice continues in Iceland today. But modern builders for the most part didn’t begin embracing green roofs until the 1960s, when European architects and scientists espoused them as a means to ease strain on taxed municipal sewer systems by absorbing stormwater. Green roofs, in contrast with traditional gravel roofs, also absorb the sun’s energy and thereby naturally reduce heat generated from the byproducts of urbanization.

Armed with this knowledge, Germany has led the green roof movement for the past five decades. According to data compiled by Temple University’s School of Environmental Design, 12 percent of all flat roofs in Germany are green. That’s largely because lawmakers there have crafted an array of incentives and regulations to encourage them.

In the United States, the practice is “only now taking root. According to a survey conducted by Green Roofs for Healthy Cities, an association of living roof businesses, the industry in North America between 2011 and 2012 grew by 24 percent, from 4.6 million square feet in 2011 to nearly 5.6 million square feet in 2012.

  • photo courtesy of Homeword Inc.

In the United States, Washington D.C. stands out for the more than 1.2 million square feet of green roof applications installed there in 2012, making it the leader among all American metropolitan regions. Coming in second is Chicago, followed by New York City. All three of those municipalities offer incentives or tax abatement to property owners who install green roofs.

In western Montana, green roofs are still “few and far between,” says Nate Lengacher, who grows mats of shallow-rooted flowering plants, mosses and succulents on his Stevensville property for living roof applications.

For $10 per square foot, locals can purchase from Lengacher’s business, Rocky Mountain Region LLC, the five layers of roofing required to construct what the industry refers to as an “extensive” living roof application. Lengacher says it’s lightweight and “made for minimal beefing up of the structure,” making it most appropriate for a residential application.

Contrasted to the deeper-rooted or “intensive” display at the Gold Dust, the lightweight living roof isn’t suited for growing food. It does, however, offer a striking display of flowering plants.

“You get whites, purples, reds, yellows,” Lengacher says. “And they flower different times of year, so the color palette is pretty dramatic…In June through July, there’s honey bees and a number of different bird species.”

Prior to installing an extensive living roof, asphalt shingles must be removed. Applications are best suited to roofs that aren’t too steep, up to what the industry refers to as an 8-12. (The typical Missoula roof ranges somewhere between a 6-12 to a 12-12 pitch, with 12-12 being the steepest). Lengacher estimates that hiring a contractor to install the layers, including a waterproofing membrane, a growing medium and the living layer, will cost an additional $4 per square foot.

Lengacher acknowledges that the installation costs may seem daunting to the average homeowner. But he says that it’s important to recognize that a living roof will outlast the typical shingled style by as much as 100 years. “That’s where the real cost savings over the lifetime of the roof come in,” he says.

He adds that this kind of project is something that a handy homeowner, one with a basic knowledge of roofing and gardening, can accomplish after doing a bit of research. And Lengacher says he’s happy to meet with locals who want to tackle an installation on their own.

“We’re happy to consult with people,” he says. “The more people who are aware that this is an option—that it’s something good for the environment and just the aesthetics of their living space—is better for us.”

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