energy efficient, to meet green building certification systems, or to be otherwise regarded as sustainable. Buildings that are not described as high-performance or green are referred to as conventional buildings.
Building standards and green building certification systems have been developed by nonprofit organizations to provide a framework for the design and operation of high-performance and green buildings. Building standards typically establish minimum requirements for the design of one aspect of a building’s performance (for example, energy). Green building certification systems, in contrast, take a “whole building” approach to design by accounting for the interrelationships among building design, materials, mechanical systems, technologies, and operating practices.
LEED, developed by the U.S. Green Building Council (USGBC), and Green Globes, licensed by the Green Building Initiative (GBI), are the green building certification systems most commonly used in the United States. EISA 2007 requires federal agencies to use a green building certification system for new construction and major renovations of buildings.
ECONOMIC PERFORMANCE METHODS AND MEASURES
Several closely related methods and measures are used for determining the economic performance of buildings, building systems, and components. There are salient differences among the methods and measures that bear on their correct application and interpretation for evaluating the cost-effectiveness of DOD construction and renovation projects.
Benefit-cost analysis (BCA) is most often used to determine if a government program or investment can be justified on economic grounds. It entails assigning monetary values to societal benefits from the program/investment, as well as to assessing direct program/investment costs, all over a specified time horizon (e.g., 20 years), and finding the difference between benefits and costs as net present value (NPV) benefits. A positive NPV means that total benefits exceed total costs, and the program or other investment is cost-effective. BCA can also be used to make mutually exclusive choices among building design, systems, and components. The choice with the highest NPV benefits is preferred on economic grounds. Related additional economic performance measures—benefit-cost ratios, internal rates of return on investment, adjusted internal rates of return on investment—can be computed from the time-denominated cash flows of benefits and costs of BCA.
Payback refers to the time period at which initial investment is recovered. Payback measures do not include future savings that may occur after the initial investment is recovered. For that reason, payback measures are not appropriate for comparing the long-term economic effectiveness of buildings or projects, because the alternative with the shortest payback period may not be the alternative with the greatest NPV benefits or the greatest return on investment.
COMPLEXITY OF THE TASK
The committee’s completion of its three related tasks was complicated by the following factors:
• Difficulty of measuring building performance objectively. The research on high-performance or green buildings inherently incorporates some level of subjectivity because of the unique nature of buildings, diversity in baselines for comparison studies, and the lack of a standard protocol for research on this topic.
All buildings differ in terms of location, materials, design, size, function, technologies, operational practices, and other factors, which influence overall building performance. The diversity in building