Heat Island Effect
From Swikipedia
Introduction
Heat Island Effect occurs when temperatures in the built-up areas is higher than nearby rural areas. The annual mean air temperature of a city with 1 million people or more can be 1–3°C (1.8–5.4°F) warmer than its surroundings. In the evening, the difference can be as high as 12°C (22°F). Heat islands can affect communities by increasing summertime peak energy demand, air conditioning costs, air pollution and greenhouse gas emissions, heat-related illness and mortality, and water quality.
Brief Description
Impact of Heat Island Effect
Elevated temperatures from urban heat islands, particularly during the summer, can affect a community’s environment and quality of life. While some impacts may be beneficial, such as lengthening the plant-growing season, the majority of them are negative. These impacts include:
Increased energy consumption
Elevated emissions of air pollutants and greenhouse gases
Compromised human health and comfort
Impaired water quality
Mitigation Practices
Use of high-albedo urban surfaces and planting of urban trees are inexpensive measures that can reduce summertime temperatures.
• Trees, vegetation, and green roofs can reduce heating and cooling energy use and associated air pollution and greenhouse gas emissions, remove air pollutants, store carbon, help lower the risk of heat-related illnesses and deaths, improve stormwater control and water quality, reduce noise levels, create habitats, improve aesthetic qualities, and increase property values.
• Cool roofs can lower cooling energy use, peak electricity demand, air pollution and greenhouse gas emissions, heat-related incidents, and solid waste generation due to less frequent re-roofing.
• Cool pavements can indirectly help reduce energy consumption, air pollution, and greenhouse gas emissions. Depending on the technology used, cool pavements can improve stormwater management and water quality, increase surface durability, enhance nighttime illumination, and reduce noise.
Using these strategies in combination can enhance their effectiveness. For example, installing a permeable pavement parking lot that includes shade trees can extend the longevity of the pavement and vegetation.
References:
http://www.osti.gov/bridge/servlets/purl/860475-UlHWIq/860475.PDF
