New research has many scientists more confident in the value of maintaining green roofs than ever before. Not only do green roofs – tops of building that grow plants – replenish vegetation that is normally destroyed in urban areas in favor of construction, they also help to battle climate change.
The presence of plants helps turn rainwater into water vapor, which in turn helps to cool the air. As Property Observer points out, a study in Toronto estimates that if every large roof in the city were to add plant species, the local temperature could decrease by as much as 2 degrees Celsius. Additionally, buildings capped with green roofs tend to have significantly lower summer cooling bills.
In recent years, architects have increasingly incorporated green roofs into their designs, mainly because they are trendy and add aesthetic values. Apartments in New York City buildings with green roofs can charge 16% higher rent than those with normal roofs. Scientists hope that they can help to encourage more people to follow through with this approach given the data. “Our research should give architects and designers justification that they are helping the environment by incorporating green roofs in their plans,” said Elizabeth Grant, a professor of architecture at Virginia Tech. “We are bridging the gap between science and design.”
Green roofs are also a terrific way of controlling storm water, which tends to overflow drainage systems and flood streets in urban areas. Whereas a traditional roof keeps about 6% of rainwater that falls, a green roof will retain 50% of that water. Meanwhile, green roofs that utilize a more intricate “deep substrate” system can hold on to over 80% of the rainwater.
“These systems are on the rise not just because they represent a link to the natural world that is scarce in the city, but because they work,” said Grant. “Extremes of temperature and rainfall are becoming unpredictable as climates change, and vegetated roofs help us build resilience in a rapidly changing world.”
Alas, it’s not all roses (literal or otherwise) for green roofs in various parts of the world. Texas A&M has experimented with plants atop its buildings and identified more than twelve species that thrived in this specific, elevated Texan climate. Still, attempts to incorporate green walls (plant life growing on the sides of the building) have been unsuccessful thus far. Professor of landscape architecture Bruce Dvorak isn’t discouraged that it’s not possible, though. “It’s a matter of finding out what works and what doesn’t,” he said.
Previously, Care2 has looked at the effectiveness of light-colored roofs as a way of reducing heat. While those roofs are beneficial because they deflect the heat from homes thereby reducing the need for air conditioning, they don’t necessarily help to reduce the global temperature. For that reason, scientists are beginning to state their preference for plant-focused house-toppers.
If you agree that green roofs are a part of the future and more specifically want a green roof to be part of your own future, check out Beth Buczynski’s article “How to Make Your Roof Green with Native Planets.” She links to a few websites that will help you get started, plus lists a variety of plants that are best suited for rooftop survival in your region of the country.