Reducing Heat in Urban Environments

While debate over "global winning" continues, one thing is certain cities are hot, and this past year in many parts of the country they have been hotter then ever before. It is known fact that in large metropolitan areas the temperature in the inner city can be as much as 8-10 degrees hotter than the surrounding area. These elevated temperatures create what scientists have labeled an "Urban Heat Island." Dr. Dale Quattrochi, Senior Research Scientist with the NASA Space Flight Center explains. "The defining characteristics of an Urban Heat Island are basically related to the dome of elevated temperatures that reside over a city in relationship to the surrounding rural areas. And this is caused by the surfaces in the city such as asphalt and pavement and concrete and rooftops that absorb sunlight throughout the day and re-radiate it at night."

As residents can attest to, in many cities such as Los Angeles and Houston higher urban temperatures affect air pollution and the quality of life. "Houston's a lot hotter because of the way we built it…" Says Bill White CEO of the Wedge Group a prominent builder in the Houston area. "… that heat bakes the chemicals in our air producing Ozone or smog. That hurts people's health, and of course nobody likes to live in a hotter city." In an effort to reverse some of the damage caused by Heat Islands, a new development program called "Cool Houston" is being applied across the region. The first component targeted for change is paved surfaces such as parking lots and streets. Shea Kent is a designer involved in the program. "Designers, engineers, and architects are all trying to now use things like white coating, light colored coatings on traditional hard surface paving, and they're also using innovative technologies such as porous paving, grass paved systems such as we have done at Reliant Stadium, which offers seven and a half acres of true grass covered paving that is engineered to handle parking loads"

The application of new paving technologies to surfaces is just one of the first steps in this plan of action. The Cool Houston planners next looked into an area of concern that was right over their heads -the building rooftops. Roofs throughout they city are being designed and retrofitted to reduce the temperatures. The roofing technologies that are being incorporated today to reduce the temperature of the roofs are white reflective colors and also vegetation, turning the roof into a green roof. Basically these two technologies result in reduced temperatures at the surface of the roof.

The final part of cooling down the Houston region took effect after urban heat island researchers began to understand how trees and vegetation affect the region's climate. Peter Smith with the
Texas Forest Service. "Trees in the region have some direct benefits for cooling. Trees shade parking lots and streets, and they also transpire water because they are living organisms, and that puts more moisture into the air which helps cool the surrounding air. Trees reduce carbon dioxide and other greenhouse gases. The programs that are being started include the city's effort to plant trees in our parks and on our streets, private sector contributions that help plant trees along our boulevards, our streets and neighborhoods, and then federal dollars which will plant trees on our major thoroughfares and highways."

As cities continue to grow the issues revolving around heat islands are expected to grow with them. But as city planners look into new construction methods and smarter environmental planning, they may be able to put a halt to the rising mercury level in downtown thermometers, and come up with some hot ideas for cool cities.