Sky high growth—What landscapers need to know about green roofs

Denver’s green roof ordinance could present new opportunities for landscape professionals
The EPA's regional office features a green roof, the first in Colorado, according to the agency. (Photo: EPA)

“In the first half of 2018, we built about 15 residential green roofs,” he said. “Maybe they’re taking advantage of a garage or something with a flat roof, or some area in between two structures where they want to create a place that’s a little more accessible and usable.”

Creath said that residential green roofs are part of a “very busy market.”

“It tends to be on a higher-end homes and new construction,” he noted, although “if you’re popping a top, you can build in the structural stability to do a new green roof without breaking the bank because you’re already adding structural components to it.”

Even homes with pitched roofs can have a green roof installed, Creath said. With special engineering, green roofs can be installed on roofs with a pitch up to 40 degrees, he noted.

Green-roof ‘workhorse’

Sedums and succulents are among the most successful plant types for green roofs, Heggem said, thanks to their root structure and tolerance for drought and wind. However, designers and landscape architects have several options to choose from.

“There are a lot of other choices as long as there’s soil and other infrastructure to support those plant choices,” she said. “It really depends on the type of green roof that you’re doing, whether it’s intensive or extensive.”

Intensive green roofs use deeper planting mediums that allow for longer root systems. Extensive green roofs typically involve shallower mediums of six inches or less.

[Related: Understanding green roofs and water sustainability]

“That soil depth really determines what you’re able to do,” Heggem added. “Those types of root systems depend on a lot of things like structural load.”

Although sedums are the “workhorse of the green-roofing world,” Creath said, he noted that in the Denver market, they may struggle in higher temperatures we have on rooftops here.

His firm has installed special irrigation systems to make sure they can keep roof temperatures cool, but they’ve also incorporated a lot of native plants and grasses.

“We use a lot of local and native plants that do well in Colorado because they grow in a very similar type of growing media, where they grow in broken-down granite and pine mulch. Our foothills are very similar to the aggregate base green-roof media that we grow them in on the roofs.”

Danielle Andrus

Danielle Andrus is the managing editor of Colorado Builder. She can be reached at [email protected].

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