Green Rooftops

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.

RoofBloom green roof demonstration trailer roams the Twin Cities, showing how a green roof can work on a garage, porch, or other small structure.