Things Are Heating Up: The Urban Heat Island Effect & Your Roof

Around half of the world�s human population currently lives in urban areas, and the scenario for the future doesn�t look like people are going to be moving away from the cities anytime soon. In fact, experts predict a 70% global increase in urban population by as early as 2030, as more and more people continue to migrate from the rural to the urban/suburban areas.

  
It�s long been established that urbanization has a major impact on air quality and climate, both over the city and the surrounding countryside. In spite of this fact, humankind continues to build infrastructure that causes our natural landscape to recede even further; as a consequence, the issue of climate control has reached critical levels. 

What Is The Urban Island Effect? 

The phenomenon that the US Environmental Protection Agency (EPA) calls the �urban island� effect refers to urbanregions or �islands� that become warmer than their rural surroundings becauseof  the buildings, roads, and otherinfrastructure that replace open land and vegetation.
 The building of cities alters the character of the natural landscape and creates microclimates where heat islands occur. Rural areas have exposed soil, grass, and trees that mitigate the high temperatures on both the air and ground level by creating shade as well as releasing the water and heat back to the air. Urban  landscape features, on the other hand, are made mostly of impermeable and heat-trapping materials that retain heat differently than vegetation, and allow less water to penetrate the soil and evaporate into the air.
 This, in general, is why cities of concrete, asphalt, glass and metal tend to absorb and store twice as much heat as a neighboring rural area. The heat island effect may result in a difference of up to 12�C in air temperature.

Cooling Off Your Roof

The first real line of defense against the heat is a building's roof. Roofing materials and colors impact how buildings and houses handle heating and cooling. It�s one of the first and most important of steps to mitigating the urban island effect.
 In the same way that people usually wear light-colored or white clothing to keep themselves cool, dark-colored roofs retain much more heat than light-colored roofs. Light colors reflect heat and sunlight while dark colors absorb and retain them. Cool roofs should have high solar reflectance as well as thermal emittance to dissipate the heat faster. This is why these so-called coolroofs are mainly painted or finished in bright white. If you�ve ever worn a black shirt in warm weather, you already know just how inefficient dark colors can be in both of these aspects.

Lighter-toned slate, while expensive, can help in reducing the heat because of its natural reflective properties. And as even naturally light-colored clay tiles on ancient structures have survived relentless centuries baking in the sun, they are great options as well. Want something a little less expensive than slate and clay? Consider concrete; it�s heavy and takes a long time to heat, making it ideal for warm weather roofing.

You can calculate just how well your roof is performing here (http://rsc.ornl.gov/), or consult with your local professional roofing contractor directly to learn more. Author Bio
Jesse Curry is a professional roofing contractor and the owner of Roofing by Curry based in Florida. His greatest strengths are his creativity, drive and leadership. He thrives on challenges, particularly those that expand the company�s reach. He is very passionate about what he does, and loves to share his experiences with other people through his blog site: http://www.roofingbycurry.com/our-blog/. 

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