This class will explain mandatory and prescriptive requirements related to duct installation, insulation, sealing, and testing, as well as requirements for heating, cooling, and hot water systems and controls. The class will also discuss mandatory requirements for mechanical ventilation and the building science rationale for these requirements. Attendees will also learn about code lighting requirements. An emphasis will be placed on explaining how these code requirements have changed through various editions of the IECC, and finally what the 2021 IECC requires.