Santa Clara University

sustainability at scu

Living Green Roof

Green roofs come in many different forms, but all have at least one thing in common: living material. Green roofs are considered a sustainable building feature because of their numerous benefits: reduced heating and cooling costs due to increased insulation, reduced heat load on the building, increased air quality, and protection from physical damage to the rooftop.

 Commons at Kennedy Mall Roof Commons at Kennedy Mall roof 
 Summer of 2006  Summer of 2007

The living green roof on the Commons at Kennedy Mall is a grid system. We chose five native varieties of seedum, including Sedum imergunchen, Sedum kamtschaticum, and Sedum album. Their colors range from yellows and reds to lush greens.

Roof on the Commons at Kennedy MallThe installation process was very simple: We placed the pre-planted trays on the rooftop, laid down pathways of green rubber pads for maintenance purposes, and installed a simple circular drip irrigation system to ensure that plants receive water during the summer months. The system should take two to three seasons for complete coverage.

Our choice of the depth of the trays also determined the type of foliage we could choose from – a deeper tray allows for larger plants – even trees, while a shallower tray is better suited for smaller plants.

Some benefits of a living green roof:
  • The growth medium (composed of rock and native soil) is porous and light weight. The roof system will retain the first ½ inch of rain, further reducing our need to water.
  • Green roofs reduce heating and cooling costs by up to 50% for the floor directly below the roof. Since the building is better insulated, less heat escapes during the winter and the building is cooler during the summer.
  • A green roof provides constant shade for the building, reducing the radiant heat load on the roof. Typical dark roofs absorb heat during the day and release heat at night, also known as the "heat island effect". Because plants on a green roof absorb sunlight but not heat, green roofs are not “heat islands” and do not have this warming effect on their surroundings.
  • Roof lifespan is increased because the roof itself is not exposed to the elements. The green roof acts as a shield to protect the roof from UV radiation from the sun, extreme temperature fluctuations, puncture, or other physical damage that roofs may incur.
  • The building looks nice from above! Students in the four surrounding residence halls have a nice view of green.
  • The two classrooms are very quiet – no noise from outside can be heard. This may also be due to the building's straw bale insulation.
 grid roof
The grid system is easy to replace, and allows for easy access to the roof below

 drip irrigation
Drip irrigation is installed, but hardly used