Green Roofs

Grey areas such as asphalt and concrete roof tops, roads, parking lots, and sidewalks cover as much as 70% of our most dense and sprawling cities adding to the urban heat island affect, increasing smog and dust, water runoff, and leaving little room for natural habitat.  The incorporation of green spaces, areas with soil and growing vegetation such as green roofs, can decrease these issues through temperature mediation, storm water absorption, slowing runoff, supporting biodiversity, and encouraging human health and activity.

Heat illnesses often cause death for lower income, inner city residents, the elderly, and children.  The 1995 heat wave in Chicago caused the death of 739 people in five days.1

Higher temperatures also increase the demand for electricity.

This causes a decrease in air quality as power plants dump more pollutants into the air to keep up with the demand for cooling.  Pollutants also form more readily at higher temperatures increasing smog.

Green roofs can mitigate urban heat island by increasing vegetation and surface reflectivity.  An asphalt roof can reach temperatures of 160 degrees F on a hot summer day were as green roofs rarely exceed 80 degrees.2 

Water runoff occurs because precipitation cannot infiltrate into asphalt and concrete.  Rather it runs across the surface and collects in sewage systems.  Large rainstorms can potentially overwhelm sewage systems and water treatment plants causing flooding and untreated water to overflow into waterways.  In New York City, 40 billion gallons of untreated wastewater, of which 20 percent is raw sewage, flows into waterways each year.3

Green roofs retain storm water, slowing the rate at which water enters the sewage system while filtering out contaminants. 

Green roofs can also aid in reintroducing wild life and plant species into the metropolis by providing habitat for birds and small animals and growing media for native grasses and even small trees. 

Human health and overall well being are equally affected by our environment.  Introducing green spaces to our cities provides places for relaxation, gathering, socializing, and outdoor activity. 

Other benefits of green roof systems are increased roof life spans, lower energy bills because of a green roof’s insulative qualities, and increased overall building value.

 

---

1. Katrin Scholz-Barth, “From Grey to Green: Environmental Benefits of Green Roofs” in Green Roofs: Ecological Design and Construction, ed. Siena Chrisman (Atglen, PA: Schiffer Publishing Ltd., 2005), 17.
2. Ibid.
3. Scholz-Barth, 18.
Photo 1: Whitney Parks

 

 

Comments