Modern Building with Green Roof in SpainModern building vertical garden facade with green roof, Santa Cruz de Tenerife Canary Islands 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.


  • 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


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

Design Considerations/Plans and Details

Design Guidelines and Maintenance Manual for Green Roofs in the Semi-Arid and Arid West