The green roof system at Villanova University was constructed in the summer of 2006 and has been monitored continuously since 2009. It is an approximately 575 ft2 extensive green roof with a 4” thick layer of media. In October of 2015, a real time control (RTC) cistern and irrigation system were added to further enhance runoff reduction from the building by capturing stormwater from an approximately 900 ft2 portion of adjacent traditional roof. The runoff is stored in a 500 gallon cistern and is used for irrigating the green roof during dry times. The system uses continuously collected soil moisture data and precipitation forecasts to determine when to irrigate and when to drain down the cistern prior to a storm event to increase capture volume.
A comparison of the system’s performances is presented highlighting the increased capture over the pre-retrofit system. The system’s capture capacity and passive use of collected stormwater is discussed and how they are incorporated into the overall volume reduction. In addition, a comparison of the modeled RTC performance and actual performance is presented including the factors leading to their differences analyzed. Finally, plans for moving forward with the system are presented using the lessons learned after two years of operation and looking forward to the addition of self-learning systems for predictive control.
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