"Even a small amount of green space can make actually quite a significant difference," says Peter Irga of the University of Technology, Sydney, referring to the performance of solar panels on green roof tops when compared to non-green roof tops. The difference Dr. Irga is referring to goes beyond the average 3.6 percent improvement of the solar panel output (which over eight months is the equivalent of $2,595 worth of renewable energy) to the increase in biodiversity on the rooftop, the absorption of almost nine tons of greenhouse gases, the reduction in the amount of storm water run-off and the reduction of surface temperature on the green roof compared with the roof with no plants. Counterintuitively, Irga's study showed that photovoltaic panels are less efficient when the temperatures rise above 25 degrees, and one way to maximize solar panels output is to have a green rooftop.

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