Cooler Paving Materials for Heat-Island Mitigation

Many cities suffer summer daytime temperatures greater than their suburban or rural surroundings. One of the causes of this “heat island” phenomenon is the absorption of sunlight by dark pavements. In warm climates, the urban heating damages the environment by adding to air-conditioning demand and creating smog. If urban roads, driveways and walkways were paved with light colored, and consequently cooler, materials these penalties would be diminished. However, lighter materials may cost more than the usual asphalt materials. In this report, the dollar value of potential air conditioning and smog savings from lighter pavements is estimated, and compared to the extra cost of such roads. The extra cost is minimized if the lighter-colored coating is applied as a thin layer when normal maintenance is performed. We find that, in Los Angeles, increasing the albedo from 0.1 to 0.35, could produce an air-conditioning saving of $0.012/m 2-yr. and smog savings of about $0.06/m2-yr. The present value of these savings, for the 5 year lifetime of the resurfacing, is about 5 times the annual saving, or about $0.36/m2. (The particular climate and smog problem clearly influence this result.) Thus one could purchase a “cooler” material whose extra cost is this amount, with no net expense. If roads are cooler they may also last longer and thus save money.