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FeedSky is the Limit
Twin Citians look to their rooftops for outdoor living and garden space
By Bonnie Bludgett
Photo by Dana Wheelock, Styled by Kathleen Behrens
Landscape architects and ambitious homeowners always aim to elevate gardening to a higher plane. What better way than to plant a green roof? The practical benefits have long been recognized: Early settlers survived prairie winters in well-insulated sod huts, and in Europe green-roofed barns and cottages are still kept neat and tidy during the summer months by grazing goats.
Neither sod huts nor goats are practical in an urban environment, yet twenty-first-century rooftop gardens blend sustainability, energy efficiency, and beauty, say proponents. One of them, award-winning landscape architect Tom Oslund, principal of Oslund & Associates in Minneapolis, says the sustainability argument is a no brainer. “The simple fact is, you’re using rainwater,” says Oslund. “We are one of the few cultures that totally disregards that part of the water supply.” It is better to recycle captured storm water on site than allow it to flow into the municipal waterways that provide public drinking water.
Green roofs hold water like a sponge and reduce the heat-island effect. Conventional rooftops can reach 180 degrees in the heat of summer. But add some cooling dirt and vegetation, and that temperature goes down dramatically—better for cooling costs and for the environment as a whole.
Here’s the drawback: Green roofs are tricky and expensive. Suitable rooftops, like Dave and Marian Petersons’ south Minneapolis garage, must be flat and able to support the weight of soil, vegetation, people, and the “winter deadload” also known as snow. Charlie Simmons, then senior project manager at TEA2 Architects (now principal at Swan + Simmons Architecture), designed the Petersons’ roof. According to Simmons, a green roof on a single-family home is generally three times more expensive than a conventional roof and uses significantly more structural material—such as 18-inch-thick trusses and eye joists—to support the extra weight. Plus, the water membrane technology used for green roofs is unfamiliar to many builders in Minnesota. “It’s something the contractor always raises his eyebrow at,” says Simmons.
Correctly installed, however, green rooftops sow both aesthetic and environmental benefits. James Dayton, principal of James Dayton Design and architect of The Bookman Stacks lofts in downtown Minneapolis, hired Oslund to convert a dreary garage roof into a lush greensward featuring a manicured lawn punctuated with circular stands of miscanthus and willows planted in attractive, square containers. A 40,000-gallon cistern system that collects the rainwater overflows into the nearby Mississippi River only after downpours so torrential they are known as “200-year storms.” Rehbein Environmental Solutions of Minneapolis installed the system of pipes that irrigate the plants.
Calculate carefully the pros and cons of green roofs before plunging into a project, cautions Steve Frenz, developer of the Bookman Stacks. “The upfront investment is significant, and there’s ongoing maintenance,” he says. But the energy savings add up. “Not only do we save on water, we don’t have to heat the garage. We hadn’t counted on that $10,000 a year savings.” The best thing about a green roof is the hardest to measure, of course—the pleasure it gives people coming and going from the building, and as a venue for outdoor events.
At the Washburn Mills Lofts in Minneapolis, a couple wanted to extend their glamorous penthouse, with its floor-to-ceiling windows and panoramic views of the city skyline and river, to include a landscaped terrace. Oslund knew the biggest challenge wouldn’t be getting the plants fed and watered, but finding species hardy enough to survive the winter on the roof, where conditions are much harsher than at street level. “The wind eddies up the side of the building and gathers momentum,” says Oslund, who massed ‘Karl Foerster’ feather reed grass and planted hardy junipers in containers lined with ordinary wall insulation. A Japanese maple is gingerly over-wintered and adds a sense of calm to the modernist landscape, which includes two box-like, teak-enclosed meditation rooms, a paver patio seating area, and a steel water element that Oslund designed. Overall, the landscape has earned multiple local and national design awards, demonstrating the aesthetic possibilities of green rooftops.
The roof of the Edgewater condominium project on Lake Calhoun in Minneapolis is dotted with three 220-square-foot rooftop cubes, each surrounded by small paver patios. Barring some mechanical components, the rest of the enormous rooftop is planted with tough grasses and perennials, such as native euphorbia, sedums, blazing stars, blue gramas, and three types of prickly pear cacti. Designed by Peter MacDonagh and Nathalie Hallyn of Kestral Design Group and installed by Berwald Roofing Company, both of Minneapolis, this green roof is a practical lounging space for penthouse residents.
The Petersons decided to add their rooftop garden in 1999. On the “observation deck” on top of the garage, high walls, and a generous shield of arborvitae and pine trees lend privacy and shelter the outdoor room from wind. Large squares of grass and flowering annuals set into recycled concrete pavers suggest a garden but require little upkeep.
The rooftop “yards” give the Petersons a perfect spot for reading the newspaper, entertaining, or playing with their terrier, Sadie. An outdoor kitchen and sleek stainless steel table and stylish white chairs make for comfortable, clean, and low-maintenance outdoor dining atop the two-car tuck-under garage. “It’s so serene out there, and flows right out from the kitchen,” says Peterson. “People have no idea we’re standing on top of the garage.”
Lanny and Mary Westphal’s thoughts turned roofward when they decided to make a one-room cottage the focal point of their perennial garden in rural Chaseburg, Wisconsin. The cottage got a fresh coat of paint and what appears to be a thick head of green hair. The Westphals planted turf grass on the roof and let it go shaggy. In summer, the front porch below is bedecked with flowering annuals in hanging baskets and a long window box. A stand of tall bee balm anchors the left corner and daylilies the right. The surrounding dense woodland makes the perfect backdrop for the Westphals’ fairy-tale vignette.
St. Paul residents Karen and Terry Kormann started their own adventure in rooftop gardening when they repaired their front stoop. It occurred to them that a green roof on the porch sheltering the new steps would delight passersby. It would also give the Kormanns a view of a garden from their second-floor bedroom rather than asphalt shingles. Accordingly, they obtained St. Paul’s first building permit for a green roof (no small feat), and hired late architect Jim Nestingen to help them devise a planting bed that wouldn’t leak or collapse under the weight of all that soil. Once the structure was up and solidly moored, they planted sedums, morning glories, zinnias, wild daisies, and various grasses. “Really, any annual that can tolerate a lot of sun works,” says Karen.
Bonnie Blodgett is Midwest Home’s garden columnist.
For more information on featured products or suppliers, please see our Buyer's Guide.
Neither sod huts nor goats are practical in an urban environment, yet twenty-first-century rooftop gardens blend sustainability, energy efficiency, and beauty, say proponents. One of them, award-winning landscape architect Tom Oslund, principal of Oslund & Associates in Minneapolis, says the sustainability argument is a no brainer. “The simple fact is, you’re using rainwater,” says Oslund. “We are one of the few cultures that totally disregards that part of the water supply.” It is better to recycle captured storm water on site than allow it to flow into the municipal waterways that provide public drinking water.
Green roofs hold water like a sponge and reduce the heat-island effect. Conventional rooftops can reach 180 degrees in the heat of summer. But add some cooling dirt and vegetation, and that temperature goes down dramatically—better for cooling costs and for the environment as a whole.
Here’s the drawback: Green roofs are tricky and expensive. Suitable rooftops, like Dave and Marian Petersons’ south Minneapolis garage, must be flat and able to support the weight of soil, vegetation, people, and the “winter deadload” also known as snow. Charlie Simmons, then senior project manager at TEA2 Architects (now principal at Swan + Simmons Architecture), designed the Petersons’ roof. According to Simmons, a green roof on a single-family home is generally three times more expensive than a conventional roof and uses significantly more structural material—such as 18-inch-thick trusses and eye joists—to support the extra weight. Plus, the water membrane technology used for green roofs is unfamiliar to many builders in Minnesota. “It’s something the contractor always raises his eyebrow at,” says Simmons.
Photo by Dana Wheelock
Calculate carefully the pros and cons of green roofs before plunging into a project, cautions Steve Frenz, developer of the Bookman Stacks. “The upfront investment is significant, and there’s ongoing maintenance,” he says. But the energy savings add up. “Not only do we save on water, we don’t have to heat the garage. We hadn’t counted on that $10,000 a year savings.” The best thing about a green roof is the hardest to measure, of course—the pleasure it gives people coming and going from the building, and as a venue for outdoor events.
At the Washburn Mills Lofts in Minneapolis, a couple wanted to extend their glamorous penthouse, with its floor-to-ceiling windows and panoramic views of the city skyline and river, to include a landscaped terrace. Oslund knew the biggest challenge wouldn’t be getting the plants fed and watered, but finding species hardy enough to survive the winter on the roof, where conditions are much harsher than at street level. “The wind eddies up the side of the building and gathers momentum,” says Oslund, who massed ‘Karl Foerster’ feather reed grass and planted hardy junipers in containers lined with ordinary wall insulation. A Japanese maple is gingerly over-wintered and adds a sense of calm to the modernist landscape, which includes two box-like, teak-enclosed meditation rooms, a paver patio seating area, and a steel water element that Oslund designed. Overall, the landscape has earned multiple local and national design awards, demonstrating the aesthetic possibilities of green rooftops.
Photo by Dana Wheelock
The Petersons decided to add their rooftop garden in 1999. On the “observation deck” on top of the garage, high walls, and a generous shield of arborvitae and pine trees lend privacy and shelter the outdoor room from wind. Large squares of grass and flowering annuals set into recycled concrete pavers suggest a garden but require little upkeep.
The rooftop “yards” give the Petersons a perfect spot for reading the newspaper, entertaining, or playing with their terrier, Sadie. An outdoor kitchen and sleek stainless steel table and stylish white chairs make for comfortable, clean, and low-maintenance outdoor dining atop the two-car tuck-under garage. “It’s so serene out there, and flows right out from the kitchen,” says Peterson. “People have no idea we’re standing on top of the garage.”
How green is my … rooftop?
Lanny and Mary Westphal’s thoughts turned roofward when they decided to make a one-room cottage the focal point of their perennial garden in rural Chaseburg, Wisconsin. The cottage got a fresh coat of paint and what appears to be a thick head of green hair. The Westphals planted turf grass on the roof and let it go shaggy. In summer, the front porch below is bedecked with flowering annuals in hanging baskets and a long window box. A stand of tall bee balm anchors the left corner and daylilies the right. The surrounding dense woodland makes the perfect backdrop for the Westphals’ fairy-tale vignette.
St. Paul residents Karen and Terry Kormann started their own adventure in rooftop gardening when they repaired their front stoop. It occurred to them that a green roof on the porch sheltering the new steps would delight passersby. It would also give the Kormanns a view of a garden from their second-floor bedroom rather than asphalt shingles. Accordingly, they obtained St. Paul’s first building permit for a green roof (no small feat), and hired late architect Jim Nestingen to help them devise a planting bed that wouldn’t leak or collapse under the weight of all that soil. Once the structure was up and solidly moored, they planted sedums, morning glories, zinnias, wild daisies, and various grasses. “Really, any annual that can tolerate a lot of sun works,” says Karen.
Bonnie Blodgett is Midwest Home’s garden columnist.
For more information on featured products or suppliers, please see our Buyer's Guide.
11 ISSUES (1 YEAR)
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