Each of the eleven technical chapters (3 through 13) begins with an overview, which is followed by a presentation of each subsystem. For the building envelope, subsections include fenestration, insulation, infiltration, etc. For HVAC, the subsections include heating equipment, cooling equipment, and ducts. Mandatory measures and prescriptive requirements are described within each subsection or component. These determine the stringency of the Energy Standards and are the basis of the energy budget when the performance method is used.