According to the non-profit organizations "Cool Communities and American Forests", trees, shrubs, and other plants shade buildings, intercept solar radiation, and cool the air by "evapotranspiration". Planting programs that group and effectively place trees can help reduce urban temperatures and make cities greener. Within ten to fifteen years--the time it takes a tree to grow to a useful size--trees placed in strategic locations can reduce heating and cooling costs by an average of 10-20%.

• Direct Effect:
  
  • Light colored roofs: reflect solar radiation; reduce air-conditioning use
    
  • Trees that shade buildings: reduce air-conditioning use
    
    
• Indirect Effect:
  
  • Light-colored surfaces: result in lower ambient temperature
    
  • Vegetation in a neighborhood reduces ambient temperature by evapotranspiration

Total energy savings amounted to 16.3% of the base case energy consumption. This analysis shows that the heat island measures would achieve a 14% reduction in peak power use.

Preliminary estimates of NOx reductions for heat island measures in the Houston Metroplex as determined by David Hitchcock of the Houston Advanced Research Center:

These estimates are based on county information provided by EPA for Reliant Energy; the pounds of NOx per MWh varies by electricity provider from 1.59 to 3.66 depending on the amount of generation fueled by coal.