While green roofs can be more expensive than traditional roofing systems, choosing a green roof has multiple benefits ranging from lower cooling costs, reducing heat loads, capturing storm water run-off and in cities helping to reduce the heat island effect. Green roofing systems come in many designs to meet your specific roofing needs.

The two most general types of green roofs are intensive and extensive. Intensive types generally are more complex and require more design expertise, but exhibit greater plant diversity such as actual parks or pedestrian garden walks. Roof depths are a foot at minimum with 80 to 120 pounds of saturated weight per square foot. An example such one is the Millennium Park in Chicago, the world’s largest green roof at 24.5 acres.

On the lighter side, extensive green roof types are 12 to 50 pounds of saturated weight per square foot and are only 1 to 5 inches deep. These types are not meant to be walked on or designed for public access. In Boise, Idaho BSU’s COBE building had an extensive green roofing system installed by Upson Company.

Plant choice should be done with care taking into consideration the climate and what types of plants are self-sustaining for the specific location. For Boise, Idaho and the surrounding Treasure Valley drought tolerant plants would be ideal. If non-self-sustaining plants are used irrigation will be necessary and a maintenance crew to monitor and maintain the plants will be necessary. A live roof that is dead and dried out becomes a fire hazard.

Some new construction projects are adopting green roofs. However, older roofs can be retrofitted with a green roofing system as long as a qualified engineer or architect is part of the retrofit. Their expertise will be necessary to ensure weight capacity limits for the structure are not exceeded. With experience in green roofing systems Upson Company is qualified to install green roofs.

http://www.facilitiesnet.com/roofing/topic/Green-Roof-Systems-Explained–19906