Is it Hot Out Here, or is it Just the Urban Heat Island Effect?

Sustainable building practices improve the health and safety of our planet.  As the world’s population grows⁠ and cities expand⁠, these practices become even more important as the risk of harmful man-made situations⁠—such as urban heat islands⁠—increase.

Image courtesy of Green Ribbon.

What is an Urban Heat Island?

An urban heat island occurs in cities when the natural landscape is replaced by pavement, buildings, and other surfaces that absorb and retain heat.  As a result, the materials create a hotter environment than rural areas. Temperatures can range from one to three degrees hotter during the day, and from three to seven degrees hotter at night!  This “heat island effect” leads to increased energy costs, air pollution levels, and heat-related illnesses.

These temperatures are influenced by the materials used, as each has an associated Solar Reflectance Index value.

What is a Solar Reflectance Index (SRI) Value?

A material’s SRI value is a way to measure its ability to stay cool by reflecting⁠—rather than absorbing—solar heat.  It’s measured on a scale from 0 to 100; a standard black surface has a SRI of 0 and a standard white surface has a SRI of 100.  The higher a material’s SRI, the lower its contribution to the heat island effect.


Under the United States Green Building Council, a building material must have a SRI value of 29 or higher to qualify for a LEED credit.

What Are Other Ways to Reduce the Urban Heat Island Effect?

The Environmental Protection Agency recommends a few strategies for reducing the urban heat island effect.  One strategy is using paving materials that tend to remain cooler than conventional pavements, such as permeable ones.  Permeable paving materials are generally lighter in color, are able to absorb and filter water, and have open pores—all features that contribute toward a cooler paving material. Permeable paving materials are also an excellent solution because they are not a one-trick pony.  They can also lower tire noise, provide better traction, and aid stormwater management.

There are a handful of permeable paving options available, including our personal favorite: GraniteCrete.  GraniteCrete has long been a champion for the environment, and we are proud to offer a product that puts it—and sustainability—first.