ABSTRACT
A typical building is designed for a forty-year economic life. This implies that the existing inventory of
buildings-with all their good and bad features-is turned over very slowly. Today, we know it is cost-
effective to design a high degree of energy efficiency into new buildings because the savings on operating
and maintenance costs will repay the initial investment many times over. Many technological advances
have occurred in the last two decades, resulting in striking reductions in the energy usage required to
operate buildings safely and comfortably. An added benefit of these developments is the reduction in air
pollution, which has occurred as a result of generating less electricity.
