Rooftop planting offers a host of benefits to urban environment

A balloonist floating over Manchester City Hall's Connector Building might look down on an expanse of perennial flowering plants growing in rooftop containers and think, "How lovely!"

But "green roofs" like this GreenGrid System deliver many benefits, both to the building below and to the overall urban environment.

UNH Cooperative Extension conceived the idea for the demonstration project and began recruiting partners from the Manchester community in 2002. The essential project components--an appropriate site, city approval, and funding--finally came together last May, enabling us to us to move forward and get the roof in place.

Benefits of a green roof
Most of the rain that hits a conventional city building's roof flows off over pavement and into storm drains, carrying pollutants such as gasoline, oil, antifreeze, sand and trash.

The GreenGrid roof will absorb up to 95 percent of an average rainfall. By slowly percolating through the plants and soil of the green roof, roof runoff occurs several hours after peak flows, giving sewer systems time to handle other runoff.

The plants and soils in a green roof serve many other functions, which include:

• Reducing the energy needed to heat and cool the building below.
• Saving money by extending the life of the original roof.
• Filtering air pollutants.
• Improving air quality.
• Absorbing noise.
• Reducing the risk of flooding and overflowing sewers.
• Providing habitat for butterflies and other pollinators.

The green roof components

• Four-inch deep containers manufactured from recycled plastic.
• Lightweight growing mix.
• Perennial plants in this system--sedums and chives--which withstand extremes of temperature and precipitation, and require almost no maintenance.

• The GreenGrid System didn't require any roof construction or redesign.
• Workers placed a slip sheet on top of original roof.
• Then they lifted the pre-planted containers into place.
• Installation took two hours.

Watch a slide show of the entire process, from filling planters to final installation on roof. Show includes both text captions and audio.

The Manchester City Web site will provide updates on the green roof, including updates on temperature monitoring and pollutant absorption.

Check out our project sign, soon to go up in City Hall Plaza

Learn more
U.S. Environmental Protection Agency's Green Roof page
Green Roofs/Healthy Cities Network
Penn State's Center for Green Roof Research
Michigan State's Green Roof Research Program
ecogeek Cool photos!

By Mary Tebo, UNH Cooperative Extension community forestry educator and Green Roof Demonstration Project coordinator

Manchester Green Roof Project Funders

UNH Cooperative Extension in partnership with N.H. Division of Forests and Lands and USDA Forest Service
TFMoran Inc.
McLane Law Firm
Manchester Development Corporation
Lavallee Brensinger Architects Fund of the N.H. Charitable Foundation, Manchester Region
Weston Solutions, Inc.
N.H. Dept. of Environmental Services
Anonymous Fund of the N.H. Charitable Foundation
Breathe NH
SEPP - Enterprise Fund, administered by the City of Manchester Environmental Protection Division

In-kind Supporters

City of Manchester
Intown Manchester
Greater Manchester Chamber of Commerce
UNH Manchester
Posted September 19, 2007