Green roofs are becoming a more popular choice for flat and low slope roofs. Green roofs are roofs that are covered in a planting medium and varying forms of vegetation. They are utilized for their insulating abilities, their ability to cool and clean the air around them, and bring more aesthetic value, including wildlife to a building.

There are many drawbacks to green roofs, they can be very expensive, need additional support, and it is hard to judge what matter of medium and vegetation makes for an effective green roof. But researchers and architects at Virginia Tech have come up with in depth studies to figure out which kind of green roofs can be productive in this manner.

Elizabeth J. Grant, an assistant professor of architecture at Virginia Tech, along with Kenneth Black and Jim Jones of the school will be releasing new reports on the effectiveness of different levels of green roofs against heat, storm run off, noise reduction at The International Conference on Building Envelope Systems and Technology in Germany.

The general idea of the study is to give architects easier solutions and reasons to begin incorporating more green roofs into their design. Grant released a statement behind the reason for the study, “… It is crucial to give architects and builders tools to make good decisions about green roofs,” and added, “Vegetated roofs help us build resilience in a rapidly changing world.”

In their study, the researchers built a variety of platforms that included varying degrees of vegetation depth ranging from 2.5 to 6 inches deep. The platforms were paired with weather monitoring tools such as temperature gauges and rain monitors and left to sit out for the period of 74 events of precipitation.

The platforms that were treated with vegetation and planting medium were much better at retaining water to reduce storm water run off. The platforms with vegetation averaged a water retention rate of about 50% compared to 6%. There are numerous benefits of retaining water, it can keep help keep storm drains clear and help cool buildings.

The green roofs proved much more effective than cool or reflective roofing materials in reducing heat in urban areas as well.