What do you want from your green roof?

All green roofs include multiple underlayers of materials that, together, protect the building and provide the conditions for the top-layer plantings to thrive.

Chief among these layers are geosynthetic materials required for separation, waterproofing, and drainage.

This article includes selections from “Green roof design and installation” by Angie Durhman, Green Roof Program Manager at TectaAmerica, at a symposium during the 2009 IFAI Expo in San Diego. Angie Durham can be reached at angie@greenroof.com.

Target Center, Minneapolis

• Largest extensive green roof on an existing building in the world
• 1st green roof on an arena building
• 5th-largest green roof in North America
• 10th-largest green roof in the world
• Used a proven waterproofing membrane
• Included a leak-detection system
• Features a 2.5-in.-thick growth zone in the center, 3.5in. around the perimeter
• Has a guaranteed 20-year maintenance contract
• Reduces the roof’s temperature by as much as 80°F
• Is designed to attract Karner blue butterflies, an endangered species