Green Roofing Systems

A green roof, or living roof, is a roof of a building that is partially or completely covered with vegetation and a growing medium planted over a waterproofing membrane. It may also include additional layers such as a root barrier and drainage and irrigation systems. 

• ENERGY EFFICIENCY - The greater insulation offered by green roofs can reduce the amount of energy needed to moderate the temperature of a building, as roofs are the site of the greatest heat loss in the winter and the hottest temperatures in the summer. For example, research published by the National Research Council of Canada found that an extensive green roof reduced the daily energy demand for air conditioning in the summer by over 75% (Liu 2003).
  
  
• INCREASED ROOFING MEMBRANE DURABILITY - The presence of a green roof decreases the exposure of waterproofing membranes to large temperature fluctuations that can cause micro-tearing and ultraviolet radiation.
  
  
• FIRE RETARDATION - Green roofs have a much lower burning heat load (the heat generated when a substance burns) than do conventional roofs (Koehler 2004).
  
  
• REDUCTION OF ELECTROMAGNETIC RADIATION - Green roofs are capable of reducing electromagnetic radiation penetration by 99.4% (Herman 2003).
  
  
• NOISE REDUCTION - Green roofs have excellent noise attenuation, especially for low-frequency sounds. An extensive green roof can reduce sound from outside by 40 decibels, while an intensive green roof can reduce sound by 46 to 50 decibels (Peck et al. 1999).
  
  
• STORMWATER MANAGEMENT - With green roofs, water is stored by the substrate and then taken up by the plants from where it is returned to the atmosphere through transpiration and evaporation.
• In summer, green roofs can retain 70 to 90% of the precipitation that falls on them.
• In winter, green roofs can retain between 25 and 40% of the precipitation that falls on them.
• Green roofs not only retain rainwater but also moderate the temperature of the water and act as natural filters for any of the water that happens to run off.
• Green roofs reduce the amount of stormwater runoff and also delay the time at which runoff occurs, resulting in decreased stress on sewer systems at peak flow periods.