The first study to compare the performance of different types of green roofs has been completed by The Lady Bird Johnson Wildflower Center at The University of Texas at Austin and suggests that buyers shouldn't assume these roofs are created equal.
Interest in vegetated roofs has increased as water and energy conservation becomes more important to property owners. Yet the study of six different manufacturers' products found the green roofs varied greatly in capabilities such as how much they cooled down a building's interior and how much rainwater they captured during downpours.
"Just having a green roof may not mean anything in terms of preventing water from reaching the street level, for instance," said Dr. Mark Simmons, a center ecologist and the lead investigator on the study. "Green roofs have to be done right, and our hope is to help manufacturers understand how to improve their designs."
Simmons and collaborators published their findings online Friday on the Web site of the journal Urban Ecosystems. They continue to review real-time temperature and other data from the study.
Wildflower Center staff designed the first commercial green roof in Austin at the Escarpment Village Starbuck's. Simmons, center colleagues and Brian Gardiner from Austech Roof Consultants Inc. simulated green roof conditions by studying the manufacturers' roofs atop metal insulated boxes. The study of 24 experimental roof tops during fall 2006 and spring 2007 at the center suggested a green roof could reduce a building's air conditioning bills about 21 percent compared to traditional, tar-based black-top roofs.
During one 91-degree day of the study, for example, a black topped box without air conditioning reached 129 degrees inside. Meanwhile, the green roof replicas produced indoor temperatures of 97 to 100 degrees Fahrenheit.
"That's a huge difference t
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| Contact: Barbra Rodriguez brodriguez@wildflower.org 512-589-8561 University of Texas at Austin Source:Eurekalert |