Green Roofs: New Spin on an Old Idea

By astaudt

In this day and age, we spend a lot of time talking about “green technology.” Sometimes the “green” is meant to indicate environmental benefit. Green roofs are environmentally friendly but they are also literally “green” in the sense that they are made up of actual living plants!

Green Roofs 02Growing living plants on your roof seems like such a bold and daring innovation that it must be a new idea. In actuality, green roofs have been around for centuries. Like all other technologies, however, green roofs have evolved and improved over time. Modern green roofs are meticulously designed to be much lighter and thinner than their historical counterparts. And our own understanding of the science behind green roofs as well as a growing concern over environmental threats has given a deeper appreciation of the benefits green roofs can offer our homes, our environment, and our society.

Urban environments, for example, suffer from what is called the “heat island effect” – essentially the elevated temperatures resulting from the roofs and pavement found in cities. Green roofs combat this in a few ways. First, the plants themselves attract and hold less energy from the sun than a tar roof or even a shingle. And green roofs can actually reduce the temperature in the air around them. Through a process called “evapotranspiration” (the combined effect of evaporation from the soil and the “breathing” or transpiration of the plant itself), the green roof can directly combat the heat island effect! And the roof itself adds a layer of insulation to the structure that any building could benefit from.

Green Roof Garden WikiWhen a large rainfall event occurs in an urban environment, the water has fewer places to infiltrate the earth. The result is that water enters the storm sewers in much higher volume – causing problems with flash flooding, water pollution, and depending on the city’s infrastructure, potentially overwhelming the city’s ability to keep storm water and wastewater separate. Green roofs can catch and hold more of that rainfall delaying the runoff enough to effectively reduce the overall spike in volume experienced by sewer systems.

Green roofs make us healthier, too. They filter the water that passes through and scrub the air around, reducing the pollutants in the environment. It almost goes without saying, but green roofs beautify as well.
20 Public Library Living Green Roof Des Moines Iowa

Even though green roofs offer many benefits, you should still consult with an expert before deciding to install one. Modern green roofs are carefully constructed with many specific layers designed to maximize their effectiveness, minimize their weight, and make sure roots cannot break through the membrane and produce leaks. And you should also make sure your roof is strong enough to bear the extra weight!

The next time you travel, keep an eye out to the skyline! Green roofs are starting to appear more and more frequently in America. And why not? Green roofs are beautiful and useful. Learn more about green roofs here: