Any building project, whether new construction or retrofit, is first subject to state laws and/or local ordinances. These laws and ordinances in turn reference codes governing a number of issues that affect the design and construction of HVAC duct systems, among them building safety, indoor environmental quality and energy conservation.

These building codes, in turn, reference standards that set forth how building materials and systems shall be manufactured, fabricated, installed, and tested to ensure compliance with code requirements. Incorporated into state laws and local ordinances, these codes and standards thus have the force of law.