What interesting times we live in! I read an article in "The Economic Times," an Indian newspaper, titled "Green Roofs differ in Capacity to Cool Interiors." It discusses the green roof studies going on a the University of Texas.
At UT, there is the Lady Bird Johnson Wildflower Center that is hosting how different types of roofs impact temperature inside structures. In particular, they have built several identical steel structures and put different kinds of roofs on them and are measuring the temperatures and water retention.
Studies are clearly indicating that green roofs definitely reduce internal temperatures. From the article:
"During one 91-degree day, ... a black topped box without air conditioning reached 129º inside. Meanwhile, the green roof replicas produced indoor temperatures of 97 to 100 degrees F. "That's a huge difference to have a 20-or-so degree temperature drop," Simmons said, noting that green roofs' ... are also believed to double the lifespan of roofing material. "
However, in places like India and Texas, where flash flooding and storm water runoff are serious issues, different green roof materials perform better than others. Again, from the article, "Yet this feature varied the most among the six manufacturers. The better green roofs retained all of the water during a half-an-inch rainfall, and just under half the water when two inches of rain fell. "
Let's hope that the studies at UT, combined with the innovation in synthetic soil by Suntory, will spread the acceptance and use of green roofs world wide, as their ability to reduce air pollution and storm water runoff make a real difference!