Glossary of Terms

Heat Island Effect

A measurable increase in ambient urban air temperatures resulting primarily from the substitution of vegetation with buildings, road and parking surfaces and other heat-absorbing infrastructure. The difference between urban areas and the surrounding suburban or rural areas can be as much as 10 degrees. Nearly 40 percent of that increase is due to the prevalence of dark roofs, with the balance coming from dark pavement and the declining presence of vegetation. Relative to remedying the other sources of the problem, replacing dark roofing requires the least amount of investment for the most immediate return.