Codes and standards (I’ll use the terms somewhat interchangeably here, although codes generally are regarded as standards that have been enacted into law) related to construction traditionally have been either prescriptive—meaning they provide a specific set of measures required for compliance, such as the characteristics of the components or materials to be used—or performance-based—meaning they define ultimate objectives and results without specifying the methodology for achievement—in nature. Both have advantages and disadvantages. Prescriptive codes, for instance, eliminate ambiguities that can result in differences in interpretation, but compliance often can be difficult and costly. Performance-based codes, on the other hand, are technology-neutral, allowing for flexibility in solutions, but may have attributes that are difficult to define.
Some codes—energy codes in particular—offer both prescriptive and performance paths as options. ANSI/ASHRAE/IES 90.1, Energy Standard for Buildings Except Low-Rise Residential Buildings, for example, primarily is a prescriptive-based standard, but provides the Energy Cost Budget Method as an alternative to its prescriptive provisions. Some green-building rating systems, which generally reference existing standards, rather than promulgate their own, also offer both prescriptive and performance paths for compliance. Green Globes for New Construction, for instance, provides that option in several categories, including exterior-light pollution, building assemblies, and interior fit-outs. In the case of exterior-light pollution, should a project team wish to pursue the prescriptive path for compliance, it must meet specific limits on total site lumens, ratings and installation requirements for luminaires, and requirements for light shielding. The performance path, however, simply specifies the total installed lumens of all lighting systems not exceed the allowable total initial site lumens permitted by the IDA/IES Model Lighting Ordinance.
Until the early 1990s, most U.S. building regulations were based on one of three model building codes. These codes were developed by Building Officials Code Administrators International, which served primarily the East and Midwest; Southern Building Code Congress International, which served the Southeast; and the International Conference of Building Officials, which served mostly the West. In 1994, the organizations joined forces to form the International Code Council (ICC), which today publishes a number of building and energy-related codes that have been adopted by local jurisdictions throughout the country. One of those codes, the International Green Construction Code, now has an alternate outcome-based compliance path, which may represent the next step in the evolution of codes in general and energy codes in particular.
An outcome-based energy code would establish a target energy-use level for a facility and provide for the ongoing measurement and reporting of the building’s actual energy use. It could be significantly more flexible than even a performance-based code, as it could be applied to a broad range of building types, including historic buildings. An outcome-based energy code would provide a metric reflecting the actual quality of a building’s energy-efficiency characteristics.
In the construction industry, the term “code” also is used in reference to zoning regulations. While conventional zoning addresses factors such as density use, floor-area ratio, setbacks, parking requirements, and maximum building height, a newer type of land-development regulation known as form-based code encourages predictable building results and a higher-quality neighborhood by using physical form, rather than separation of uses, as the organizing principle. In other words, a form-based code specifies such attributes as street and building type (or mix of types), build-to lines, number of floors, and percentage of building-site frontage.
As HVAC professionals, we always are going to have to comply with various codes and standards. It’s important to understand both where those codes and standards are and where they’re headed.