Albedo is the fraction of incoming sunlight that a surface reflects, measured from 0 (absorbs everything) to 1 (reflects everything).
Parking lots are among the largest dark surfaces in a city. Fresh asphalt reflects very little sunlight, often around 5 percent, rising somewhat as it ages and lightens; new concrete typically reflects far more, often 25 to 40 percent. Dark pavement absorbs heat by day and releases it at night, contributing to the urban heat island effect.
Related measures
- Solar reflectance is the technical term for albedo used in building standards.
- Solar reflectance index (SRI) combines reflectance and how well a surface sheds heat.
- Green building programs such as LEED and Parksmart reward high-SRI paving and roofs.
Ways to raise it
- Concrete or light-colored pavement on surface lots and garage roofs.
- Reflective coatings on existing asphalt.
- Shade from trees or solar canopies, which also generate power.
- Vegetated roofs on garage top decks. See green roofs.
The Parkonomics view
A surface lot is a heat collector by default. Shading it with solar canopies turns the problem into a power source.
Related terms: Heat Island Effect, Solar Canopy, Green Roofs, Parksmart Certification, Stormwater Detention, Sustainability