[Expert Article] Green Roofs

As cities grow rapidly, more buildings are being built in higher altitudes. Buildings are replacing what have once been grasslands and forests, raising the local temperatures of such metropolitan areas. When we take a look at the conventional roof in an urban environment, it is often a barren concrete desert with unfavorable conditions such as high temperature contrasts and harsh winds. To mitigate the various environmental issues we’re facing, we want to make a reverse turn and transform these concrete deserts back into grasslands, this time at elevated levels.

   

Historically, green roofs have appeared on the prairies—sod houses constructed with the sod of thickly-rooted prairie grass. These living roofs were invented because of the lack of other building materials like wood or stones. Nowadays, architects and planners increasingly turn to green roofs not because of shortage of building materials but for aesthetic and environmental reasons.

Benefits of Green Roofs

   

• Reduced energy use and air pollution 
• Enhanced human health and comfort
• Improved storm water management 
• Revamped look for a lackluster rooftop

It is no news that air pollution has been a problem in cities. Green roofs add layers of insulation to buildings, thereby reducing the energy used for cooling and heating systems.  They also cut down air pollution, since air conditioning is directly linked to greenhouse gas emissions. In addition, vegetation cleans the air by removing air pollutants through dry deposition and carbon sequestration (epa.gov).

Urban heat island describes the condition in which cities are hotter than the surrounding rural areas. Because cities tend to have a lot more dark surfaces and fewer green covers, more heat is absorbed. According to EPA statistics, the annual mean temperature of a city with one million or more can be 1.8-5.4°F warmer than its surroundings. In New York City’s case, it is 7°F hotter than Westchester suburbs. Green roofs alleviate this issue by providing shade and removing heat through evapotranspiration.

Green roofs reduce storm water runoff and filter pollutants from rainfalls. In cities that rain often, rainwater can overflow the sewer and causes pollution and diseases.

A rooftop garden allows city dwellers quick retreats from the bustling city, being right above their apartment home or office. In contrast to the dreary concrete rooftop, green roofs are like a breeze of fresh air in city dwelling.

Taking it to the Next Level: Rooftop Farming

Elevated Park: The High Line, New York

The green strip that runs across Manhattan is a repurposing of the obsolete railway called the West Side Line. The project was constructed in three phases, and took approximately ten years to complete, from initial idea to realization.

Works Cited

"Green Roofs." EPA United States Environmental Protection Agency. N.p., n.d. Web. 01 June 2015. <http://www.epa.gov/heatisland/mitigation/greenroofs.htm>"HIGH LINE." BuroHappold Engineering. N.p., n.d. Web. 01 June 2015.<http://www.burohappold.com/projects/project/high-line-160/>