05/17/2005

Urban Heat Islands: What You Can Do Now

The Environmental Protection Agency offers an explanation as well as helpful advice

Contributors: James Earl  
 

If mention of urban heat islands has you scratching your head, the confusion ends now. The U.S. Environmental Protection Agency (EPA) offers some basic information and helpful tips on how you can help mitigate the problem of urban heat islands. According to the EPA, “Heat islands are characterized by urban air and surface temperatures that are higher than nearby rural areas.” The cause of this rise in urban temperatures is a result of the following:

  • A reduction in the amount of trees and vegetation in urban environments, which minimizes cooling from shade and evaporation of water from soil and leaves.
  • High-rise buildings combined with narrow streets trap heat between them and reduce wind flow.
  • Vehicles, factories, and air-conditioners produce waste heat that adds warmth to the air.

Aside from elevated summertime temperatures, the negative effects of urban heat islands range from increased peak energy demand and air-conditioning costs, to higher air pollution levels and heat-related illness and fatalities.

Communities can reduce the effects of urban heat islands in four ways - cool roofs, trees and vegetation, green (or garden) roofs, and cool pavement.

Cool Roofs
According to the EPA, “On a hot, sunny day, traditional roofing materials can reach peak temperatures of 190 degrees F. By comparison, cool roofs reach maximum temperatures of 120 degrees F.” Reducing the surface temperature of roofing materials by installing systems with high solar reflectance can result in lower energy bills, peak energy demand, and, consequently, reduced air pollution and greenhouse gas emissions.

Trees and Vegetation
The increase in a city’s vegetative cover is beneficial because in addition to cooling from direct shading, trees and plants cool the air through a process called evapotranspiration. The EPA reports that scientists at Lawrence Berkeley National Laboratory estimate planting trees and vegetation for shade can result in a 25-percent reduction in a building’s cooling energy consumption annually.

Green (or Garden) Roofs
Rooftop gardens or “green roofs” replace heat absorbing surfaces on the roof with vegetation that work to counteract the effects of urban heat islands via evapotranspiration. There are two types of green roofs - intensive and extensive - that are distinguished by the amount of soil and plant cover installed on the roof. “This reduces summertime AC demand by lowering heat gain to the building,” reports the EPA.

Cool Pavement
While the EPA reports that cool paving research is still in its infancy, early studies show that large parking areas, terminal facilities, airfields, and urban roadways with large expanses of paved surface may be practical applications. With a higher solar reflectance, cool paving materials (although not mandated by any standard or labeling program) can lower surface temperature and even allow stormwater to pass through.

This information was excerpted from the U.S. Environmental Protection Agency’s informative brochure “Cooling Summertime Temperatures: Strategies to Reduce Urban Heat Islands.” For more information, visit (www.epa.gov/heatisland).

 

 


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Visit our website today to learn about the design flexibility of a Morton building and the endless possibilities of partnering with our designBUILD team.


Wood construction is both cost and energy efficient. Check out Morton Buildings and our designBUILD team online today to discover all the benefits of post-frame construction.


When choosing a metal-clad building for your next construction project, consider Morton Buildings, Inc., and their designBUILD team, we’ll make your dream a reality.

We Can Help You Reduce Energy by 30%

Our mission is to help our customers manage their buildings' energy costs, improve reliability, and enhance performance while having a positive impact on the environment.
CLICK HERE to find out how.

Add highly responsive multi-zone comfort to any building project, in any climate. Our CITY MULTI H2i R2- and Y-Series VRF systems give you flexibility to fit the needs of any building. Enjoy 100% heating capacity at 0°F outdoor ambient, and 85% heating capacity at -13°F outdoor ambient.  For more information, log on to www.mitsubishipro.com

 
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