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Green Roof Stimuli
Incentives to Install Living Roofs

by Mike Dahl, LASN

Green Roof Stimuli

Vegetated, or green roofs, like the Columbia Green Technologies one at Aleutian Spray Fisheries headquarters in Seattle, can help meet the city's building code requirement of 30% plant coverage in commercial zones. In addition to assisting with city's building code and stormwater requirements, the green roof created an inviting amenity deck space for their employees. This instillation used metal edging to create clear separations between planting zones, and define locations for maintenance personnel to deadhead the spent blooms from certain swaths of sedums. (Photo Credit: Columbia Green Technologies)

Green roof construction continues to grow in popularity in North America due to the environmental benefits they provide, an increase in interest in green building and the enactment of regulations and the offer of incentives by various governmental bodies.

Aesthetics aside, the benefits of green, or vegetated roofs include better stormwater management, reduction of the urban heat island effect, removal of carbon from, and release of oxygen into, the atmosphere, added habitat for birds and insects, decreased energy costs for the building's tenants and increased life of the building's roof membrane. Of these, stormwater management seems to be the main impetus for the regulations and incentives.

In the book, The Green Roof Manual by Edmund C. Snodgrass and Linda McIntyre, the authors note "stormwater management infrastructure is overburdened in many cities, and green roofs are one way to take some of the pressure off by mitigating runoff into those systems."

Green Incentives
Chicago, an early supporter of green roofs (its city hall, under the directive of then-mayor Richard Daley, had plants installed on its topside in 2000), not only offered an expedited permitting process to developers who incorporated green roofs in their plans, they also allowed the square footage of the roof to be counted toward any pervious surface area requirement.

Portland was another early adopter, officially recognizing vegetated roofs as a stormwater best management practice in 1999. To promote their inclusion on commercial and residential structures, the city began, in 2008, offering grants of up to $5 per square foot, which amounted to about 50% of a project's overall cost according to industry specialists.

Green Roof Stimuli

This is one of five green roofs located at the Silver City Townhomes in Milwaukee where approved projects received up to $5 per square foot from the Metropolitan Sewerage District Regional Green Roof Initiative. Each roof is 2,315 square feet in area. Pre-vegetated mats with only 1.25 inches of growing medium from Xero Flor Green Roof Systems were used along with two layers of lightweight, 1/4-inch water retention/filter fleece.
PHOTO: Xero Flor America

Green Roof Stimuli

The Chicago Department of Buildings expedited building permits for projects that incorporated green building techniques, such as green roofs, and pursued LEEDA(R) certification from the USGBC. This building located in Chicago's Logan Square neighborhood features an 8-inch-deep, built-in-place green roof system planted with perennial starts and seeded with meadow plants. Its maximum saturated weight is 36 pounds per square foot.

The Regional Green Roof Initiative in Milwaukee provided funding for up to $5 per square foot of approved green roofs on properties that were within the city's sewerage district.

In 2006, Philadelphia created a new stormwater manual that contained recommendations for green roofs. The city offered stormwater fee credits for buildings that met the conditions defined in the manual, and a business tax credit of 25%, up to $100,000, of eligible green roof construction fees.

A 50% credit against stormwater usage fees was given to properties in Minneapolis that improved stormwater management systems, which includes green roof installations.

Nashville, Tennessee, reduced a building's sewer fees by $10 per square foot of green roof.

The Green Roof Tax Abatement Program in New York City offerd $4.50 per square foot of area, up to a maximum of $100,000 for a given project.

Green Roof Stimuli

Stormwater management at Frostburg State University in Maryland was improved by the Gira Center for Communications & Information Technology's green roof, which was designed by Site Resources Inc. and showcases sedums and sedges arranged in arcs around two observation platforms. Downspouts direct roof rainwater to the base of the building and then daylight the water into narrow open concrete runnels. Two counties in the state (though the university was not in either of them) offered incentives for green roof installations. Montgomery County's Rainscapes Rewards Program provided rebates up to $10,000 for approved stormwater management systems, and Anne Arundel County allowed a tax credit of 10% of the cost of such an installation to be taken per year for five years, again up to $10,000. PHOTO: SRI

Green Roof Stimuli

Urban Associates, Inc. as a sub-consultant to CDM Smith, designed the landscape at the Administration and Visitor Center at the Solid Waste Authority located in West Palm Beach, Florida. It was officially certified LEED Platinum by the USGBC and features an 8" to 14" depth intensive green roof planted with native coastal perennials and shrubs. As per design, the first flush runoff from the non-green portion of the roof is directed to a rain garden to provide stormwater quantity and quality treatment.

Green Roof Stimuli

A 16'-high "green screen" planted with jasmine was planned for the west face of the Administration and Visitor Center to reduce the heat island effect from the afternoon sun.

Government entities in Ohio received below market rate loans for the design and construction of green infrastructure on economic development projects.

Expedited permitting and low rate loans with longer payback periods were made available, through the Properly Assessed Clean Energy program, to San Francisco commercial developments that included vegetated roofs.

And in Washington, D.C., rebates for eligible green roof construction ranged from $7 to $10 per square foot.

Mandating Green Construction
San Francisco was the first place in the U.S. to enact a law calling for green roofs - requiring between 15 to 30 percent of a roof's area on most new building projects to be planted with vegetation, installed with solar panels, or a combination of both.

In 2017, voters in the city of Denver passed an initiative that required green roofs on new buildings of 25,000 square feet or more of floor area, and vegetated roof and solar panel combinations on existing buildings of that size when replacing their roofs. The city council however revised that ordinance; adding compliance options that would produce environmental benefits at less cost.

Green Roof Stimuli

At the Keep Indianapolis Beautiful headquarters, the green roof system was designed with a high-efficiency irrigation system. Once the plants are established, the roof requires as little as 50 gallons of water each day, even during the hottest, driest weather, to thrive.

Green Roof Stimuli

Green Roof Stimuli

The effort to replace Hampton Roads Transit's 100-year-old bus maintenance facilities in Norfolk, Virginia, was headed up by the design team at InSites. The LEED Gold certified project included two green roofs - one that serves as an employee break area (bottom photo).

And other places have building code requirements that the inclusion of a green roof can help satisfy. For instance:

All projects receiving financial or zoning assistance from the city of Chicago must fulfill certain green building conditions, and all new city buildings must be LEED certified.

Seattle requires 30% of plant coverage in commercial and neighborhood commercial zones and 50% coverage in multi-family residential zones.

Through the State Green Building Construction Act, all new government buildings and major renovation projects in New York must meet green building standards set by the state's Office of General Services.

San Francisco's Green Building Ordinance sets criteria for stormwater runoff amounts.

And legislative efforts continue: last year members of the New York City Council introduced various proposals that would require that the roofs of certain buildings have all or part of their available space covered with environmentally-friendly solutions such as a green roof system.

As seen in LASN magazine, January 2019.

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December 5, 2019, 7:13 am PDT

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