**9.4 Role of trees to reduce cooling costs**

The presence of trees and vegetation around and on houses and buildings is another simple proven method of keeping energy costs low (Akbari, 1992, 1997, 2001; Raeissi, 1999). Trees cool buildings both by shading the walls and roof from the sun, and by cooling the ambient temperatures by their evaporation processes. A rooftop garden on a five-story commercial building gave savings of 0.6–14.5% in the annual energy consumption (Wonga, 2003). Increasing of soil thickness and its moisture content would further reduce the building energy consumption substantially
