Energy codes have traditionally contained mandatory and prescriptive items. Mandatory measures must be complied with in all situations while prescriptive measures can be traded with other efficiency measures by following a performance path. Recent editions of the International Energy Conservation Code (IECC) also contain additional efficiency packages, where one or more optional measures must be selected to satisfy an ‘additional’ efficiency requirement. Such a structure is currently employed in section C406 of the IECC, and similar approaches have been considered for ASHRAE Standard 90.1 as well as state building codes. This approach has the advantage of providing increasing levels of performance, while maintaining flexibility in allowing the designer to optimize the most appropriate technologies and efficiency measured based on the attributes of a particular project.