Home ] What is "Cool Communities" ] About Us ] [ Cool Pavements ] Cool Roofs ][ Green Roofs ] Urban Shade Trees ] Task Force Members ]

 Cool Pavements

Pervious Pavements for a More  Livable Environment






City of Atlanta's pervious parking lot
at corner of Pryor and Memorial.

A new mind set is needed when designing stormwater management systems. Rather than designing a system to pass huge storm events (that may occur only twice a century) rapidly from an area, water management planners should consider the benefits of capturing and recharging water from the smaller, more frequent rain intervals. Atlanta, for example, receives significantly more than half its annual rainfall from precipitation events of less than an inch. The ecosystem lives and dies on daily events. A stormwater system incorporating pervious pavement will be much more effective in reducing total runoff and increasing the amount of filtered groundwater. The material's ability to retain stormwater while improving water quality and enhancing tree and vegetation growth, makes this material a very exciting example of green and sustainable building practice.

Pervious pavements are less able to absorb and store heat than conventional pavements. The lower density of the material (15 - 25% void spaces) reduced heat storage capacity. The lighter colors of some pervious pavement systems reduce the heat absorbing capacity of the pavement. The open void structure in the pervious pavement allows cooler earth temperatures from below to cool the pavement. These factors allow pervious pavement systems to approach natural ground cover in heat absorbing and storage capacity.

Unlike traditional concrete or asphalt, pervious pavements typically provide a void content of 15-25%, offering improved filtration and an enormous amount of surface area to catch oils and chemical pollutants. Some experts believe that the bacteria living in these spaces break down pollutants preventing much of the polluted runoff that normally occurs with traditional pavements. Parking lots, in particular, hold a tremendous potential for this material because of the amount of oil and other hydro-carbon liquids that seep from parked cars. In addition, if not impeded, these bacteria may lead to damages that may prompt home owners to use their mortgage for repairs and renovations.

Pervious pavements can be made of concrete, asphalt, open-celled stones, and gravel, that are mixed in a manner that creates an open cell structure allowing water and air to pass through. For example, porous concrete can pass 3-5 gallons of water per minute, which is far greater than most conceivable rain events and highly effective in controlling stormwater drainage.

Because pervious pavements allow rainwater to seep into the ground through the pavement:

  • Vegetation is watered, reducing 
    the need for irrigation
  • Ground water is recharged
  • Water resources are preserved
  • Stormwater runoff is reduced
  • Stormwater runoff quality is

The strength and durability of pervious pavement appears to be equal to traditional materials. There are several examples of parking lots built more than twenty years ago with pervious pavement that are still structurally sound and still have a high level of permeability. Pervious pavement is also less susceptible to freeze-thaw cracking, due to large void spaces.

Concerns about clogging of pervious pavements can be "designed out", by reducing erosion and sediment runoff through strategic design and water retaining ground cover. 

Look for ready mix concrete trucks with these decals

 "Concrete is Cool"

Paving with porous materials:

  • reduces storm water runoff
  • replenishes groundwater
  • reduces flooding and loading to sewage treatment plants
  • means less land set aside for retention basins
  • reduces pollutants in run-off
  • reduces irrigation requirements
  • cool water run-off temperatures
  • lessens evaporative emissions from parked cars


Atlanta Mayor Shirley Franklin dedicated the City's new "environmentally friendly" parking lot on Thursday, June 6, at 9:30 a.m.  We commend the city and all those involved in designing and installing this porous concrete parking lot that helps to manage stormwater and mitigate Atlanta's urban heat island.

More Resources Sustainable Living: