Green Roofs and Rooftop Gardens

Modern Building with Green Roof in Spain

A green roof or rooftop garden is a vegetative layer grown on a rooftop.  Green roof systems include several different layers, including structural support, vapor barrier, thermal insulation, root barrier, drainage layer, filter membrane, growing medium, and vegetation.  Use compost-amended soil for the growing medium and mulch for erosion control.

Benefits

  • Reduce heat island effect
  • Provide shade
  • Improve aesthetics
  • Reduce temperature of roof surface by up to 40 °F below conventional roofs
  • Reduce city-wide ambient air temperatures by up to 5°F
  • Reduce energy use
  • Reduce stormwater runoff
  • May qualify for credits under green building rating systems

Limitations

  • Existing structural support may not be sufficient
  • May require water supply
  • May increase insurance cost

Research