Praying mantis on PECO’s green roof.
How did it get up there?
photo by Nicole Dupree

Adjacent to PECO’s (Philadelphia Electric Company, 2301 Market Street, Philadelphia, PA ) headquarters in downtown Philadelphia is an eight story building that needed a new roof in 2009.  PECO executives wanted to replace the roof with something special and energy-saving  They looked into installing solar panels on the roof, but found that the surrounding high rises blocked sunlight for much of the day.  They decided to replace the 45,000 square foot roof with a roof meadow: an “extensive” area covered with succulent plants that can withstand harsh conditions.  These succulents, called sedums, are low growing and create a type of  living matt  for the roof.  In addition to the sedums, there are four large planters with native grasses and other perennials. The Pennsylvania Horticulture Society (PHS) maintains the roof and conducts tours on the third Tuesday of every month, April-October.  ($5.00 for PHS members, $10.00 for PHS non members) http://pennsylvaniahorticulturalsociety.org/peco-green-roof/index.html  So what is a green roof? A green roof is a roof made of multi layers of drainage systems, growing medium, and plants, on top of a waterproof membrane.  Such roofs make buildings more energy efficient.  They reduce the impact on the environment.  In the case of PECO’s green roof, about 1.6 million gallons of water is kept OUT of the aging sewer system in Philadelphia.  Temperatures on the roof in the summer are between 60 and 80 degrees cooler ( average temperature on a Philadelphia roof can be 150 degrees F or higher)