There is no denying that our buildings can get hot in the summertime. We often refer to utilizing cool roofs and reflective coatings to help reduce the surface temperatures of the roof as well as the building interior. But one phenomenon that many people aren’t as familiar with is the heat island effect. In urban or downtown areas, buildings, roads, and other manmade infrastructure absorb and subsequently release the sun’s heat – much more so in areas with natural forests or bodies of water. When structures are prevalent and greenery is scarce, “islands” of higher temperatures and pockets of extreme heat begin to materialize.

A review of U.S. research studies and data (Source: EPA) found that a heat island situation results in urban daytime temperatures that can be as much as 7°F higher than in outlying, natural areas. This effect is present even after the sun sets, with nighttime temperatures proving to be up to 5°F higher as well. Humid Southeastern cities with dense populations exhibit the most significant temperature differences. Research indicates that the heat island effect will continue to strengthen the population density of urban areas expands.

How Heat Islands Form

Heat islands tend to occur when several factors are in place. These include:

Disappearing Natural Landscapes in Urban Communities: Plants, trees, grass, and water cool the air by offering shade, absorbing water from plant leaves, and evaporating surface water. Hard, arid surfaces in urban environments – such as sidewalks, parking lots, roads, roofs, and buildings offer less shade and moisture than organic landscapes, resulting in higher temperatures.
Material Property Characteristics: The man-made materials typically used in urban environments (roofing and asphalt) tend to reflect less solar energy, absorbing and releasing more of the sun’s heat than vegetation or other natural surfaces. Heat islands tend to build throughout the daytime hours and become more prevalent after sunset as heat is slowly released from these urban materials.
Urban Geometry and Design: The spacing of buildings within a city block impacts the flow of air (wind) and the material’s ability to absorb and re-emit solar energy. In congested areas of development, surfaces, and structures blocked by neighboring structures become thermal masses that cannot easily release their heat.
Man-Made Heat Generation: Automobiles, delivery trucks, HVAC units, building structures, and industrial plants all release heat into the urban environment. These sources of anthropogenic (human generated) waste heat can contribute to heat island effects.
Weather, Climate, and Geography: Clear and uneventful weather conditions can actually cause more severe heat islands. This is because solar energy has no barrier to reaching urban surfaces, and nothing is dissipating that heat. However, robust winds and cloud cover inhibit the formation of a heat island.

How Can We Mitigate the Heat Island Effect?

There are several ways that city planners and property owners can reduce the heat island effect and positively impact the environment.

Parks, open agricultural land, and bodies of water can encourage cooler spaces within an urban environment. This is why temperatures are generally lower in suburban or rural areas than in downtown areas. Therefore, filling open spaces with water features and greenery —and even adding living green walls to the exterior of commercial spaces—can go a long way to cooling down the environment.

Those who own or manage commercial buildings should look into cool or reflective roofing to help with this issue. By coating the top of the building with a reflective material, the heat is repelled, not absorbed, allowing for a cooler surface and cooler interior. An entire neighborhood with reflective roofing can make a significant impact on the temperatures in that vicinity.

At Unicoat Industrial Roofing, we specialize in applying roof coatings that will protect your roof, extend its life span, reduce your utility expenses, and, yes, positively impact the environment. Call today to learn more.