“As urban areas grow a person’s health will be connected to the build up of heat and pollution in the city…..it will become essential to build green.”
By Linn Smith
April 20, 2017—–If you live in a city you probably have noticed how much cooler it is in the summertime when you take a drive in the country. Drive back toward the city, with its concrete buildings, and you feel the great intensiveness of a hot summer day. There’s a name for this city heat….the urban heat island effect.
What is a Heat Island?
An urban heat island describes a large area of buildings and concrete (cities) that has temperatures which are higher than the countryside surrounding them. According to http://www.epa.gov, “The annual mean air temperature of a city with 1 million people or more can be 1.8–5.4°F (1–3°C) warmer than its surroundings. In the evening, the difference can be as high as 22°F (12°C).” With global warming the temperatures of the heat islands will continue to increase.
What Causes the Build Up of Heat?
As you enter a city you may notice concrete and asphalt surrounding you—-buildings, parking lots, streets and side walks. The concrete and asphalt absorb the sun’s heat rather than reflecting it, causing surface temperatures to rise. The rise in temperature also causes a depletion of vegetation resulting in less shade and moisture in the air. The resulting heat requires an increase in energy consumption—air conditioning which results in greater electrical use. This cycle keeps revolving—a catch 22 in which there is no escape from the merry-go-round of negative conditions from heat build-up.
Smog and Heat Islands
Cities can also cause “hotspots” of pollution. This smog can trap heat over a city, holding in the gases from coal burning facilities and vehicle emissions, not allowing them to escape into the atmosphere (the greenhouse effect). In addition, the closely built structures resist air flow, keeping the air trapped in the city, unlike the countryside which cools off as the air flows more freely.
Health Effects of Heat Islands
Some of the more obvious effects of heat islands are discomfort, breathing problems, heat stroke and exhaustion. But they can also be related to cardiovascular disease, sleep deprivation, depression and many more!
Minimizing the Heat Island Effect
New technologies for minimizing heat islands are rapidly being developed. Several techniques currently in use for developing green urban areas are:
*Cut down on heat absorbing materials, such as asphalt and cement, by using more reflective surfaces for paved areas.The pavement can be enhanced by using reflective aggregate, a reflective or clear binder or a reflective surface coating.
*Plant trees that shade streets and paved areas.
*Use white roof membranes instead of black.
*Create a green roof–rooftop gardens.
*Create rooftop decks made from wood.
*Increase shade around buildings.
*Use energy efficient appliances and equipment which cut down on electrical use.
As National Geographic summarized, “Urban heat islands can have worse air and water quality than their rural neighbors. They often have lower air quality because there are more pollutants (waste products from vehicles, industry, and people) being pumped into the air. These pollutants are blocked from scattering and becoming less toxic by the urban landscape: buildings, roads, sidewalks, and parking lots.”
As urban areas grow a person’s health will be connected to the build up of heat and pollution in the city…..it will become essential to build green. The planning stage for this is now!