Big Green: Interesting comparison study on Green Roofs

[James A. Wise]

Dear BG colleagues,

In case some of  you missed this from the Chronicle for Higher  
Education--not your usual GB source.....

Cheers,

Jim W.

Study of Green Roofs Finds Some Perform Better Than Others

Green roofs can vary widely in their performance characteristics,  
researchers at the University of Texas at Austin found in a study  
comparing six manufacturers’ products. For the study, the researchers  
created 24 experimental roof samples that used varying mixes of 16  
types of plants.

The study was conducted in 2006 and 2007 by the university’s Lady  
Bird Johnson Wildflower Center, and some results were described in a  
university news release. The researchers published a full account of  
their findings on the Web site of the journal Urban Ecosystems.

All of the green roofs outperformed traditional roofs in lessening  
the need for air-conditioning. At noon today, for instance, the  
center reported on its Web page that the outdoor air temperature was  
84.9 degrees Fahrenheit. The surface temperature of a black-topped  
roof was 101.5 degrees, while the temperature below it was 101.6. The  
surface temperature of a white-topped roof was 89.2, while the  
temperature below it was 97.0. The surface temperature of a green  
roof was 82.2, and the temperature below was 89.4.

Where the green roofs differed significantly, however, was in how  
much rainwater they captured during storms, preventing the water from  
becoming runoff. Roofs with more plants native to Texas captured  
water better than those planted with sedums, which are more commonly  
used for roofs. The best roofs captured all of the water during a  
light rain and about half the water from a downpour, the researchers  
reported, whereas the least-effective roofs captured only a quarter  
of the water from a light rain and less than 10 percent of what fell  
during a deluge.

Lawrence Biemiller | Monday August 11, 2008

<http://chronicle.com/blogs/architecture/2311/study-of-green-roofs- 
finds-some-perform-better-than-others>