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Green Rooftops

Corrie Zoll
Minnesota Green Roofs Council

A green rooftop is a rooftop that incorporates plants as part of a building’s roofing system. Properly designed, green roofs are stable, living ecosystems that replicate many of the processes found in nature. Green rooftops can provide multiple ecological benefits including stormwater management, water quality improvements, reductions in energy use, air quality improvement and increased wildlife habitat.

Green rooftops are becoming more popular in the Twin Cities as building owners become aware that the ecological benefits listed above are complemented by significant economic benefits. With green rooftops, building owners can see reductions in heating and cooling costs, reductions in stormwater management costs, and a doubling of the life expectancy of a buildings roof membrane.

Minnesota is home to nearly 100 green rooftops. That’s a million square feet of live plants on top of buildings rather than hot, hard roof surfaces. Green rooftops make roof membranes last longer while reducing energy costs and managing storm water. Expect to see the number of green roofs in the state double or triple over the next decade.

Hundreds of homeowners in Minnesota are trying to figure out how to incorporate green rooftops in their own back yard. RoofBloom is a program designed to help homeowners to implement a green rooftop on a garage or other small outbuilding. RoofBloom offers workshops, demonstration sites, hands-on training, printed materials, building plans, plant lists, planting plans, and advice.

Things to Consider When Planning a Garage Green Roof:

Weight. A basic green roof adds 10-20 pounds per square foot to the weight of a roof. You’ll need a structural engineer to make sure your building is strong enough.

Waterproofing. A quality waterproof membrane is needed. A green rooftop will double or triple the life expectancy of this membrane.

Erosion control. Simple materials are available to keep plants from sliding off a pitched garage roof. Green rooftops can be installed on roofs up to a 40% grade.

Growing Medium. Green roofs use a growing medium that is engineered to be lightweight and to support green roof plants.

Plants. A wide variety of native and non-native plant species will thrive on green rooftops. The best plants for green roofs are shallow-rooted, drought-tolerant, and provide solid ground cover.

Maintenance. Someone is going to have to get up on the roof to water, pull weeds, and inspect for problems.

View a green roof near you:

  • Phillips Eco-Enterprise Center (live web cam www.greeninstitute.org)
  • Loring Greenway (parts of the path are made up of green rooftops)
  • Brit’s Pub
  • Minneapolis Central Library (a small portion is visible from the Teen section)
  • Minneapolis City Hall (spring 2007)
  • Crowne Plaza Hotel 8th floor sky garden
Read Up

Green Roof Plants, Edmund Snodgrass and Lucie Snodgrass, Timber Press, 2006.

Planting Green Roofs and Living Walls, Nigel Dunnett and Noel Kingsbury, Timber Press, 2004.

 

Act Locally
The Bakken Museum
3537 Zenith Avenue South
Minneapolis, MN
(accessible to museum visitors)

Brit’s Pub
1110 Nicollet Avenue
Minneapolis, MN
(open seasonally to customers)

Lebanon Hills Regional Park Visitors Center
860 Cliff Road, Eagan, MN
(sloped green roof can be seen from the ground outside the visitors center)

Green Rooftops

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