Promulgated by the International Code Council (ICC), this national code establishes minimum regulations for the energy efficient design and construction of both residential and commercial buildings using prescriptive and performance- related provisions. Chapters 4, 5, and 6 contain various compliance paths for residential buildings; Chapters 7 and 8 contain the same for commercial buildings.

Table 503.3.3.3 of the IECC 2003 edition contains minimum HVAC duct insulation requirements for residential buildings.

Duct insulation requirements for commercial buildings are established in Chapter 7 by reference to ANSI/ASHRAE/IESNA 90.1-2001, tables 6.2.4.2a and 6.2.4.2b. The IECC 2000 Edition references ASHRAE/IESNA 90.1-1989, table 9.2. Finally, Section 803.2.8 contains the following alternate commercial duct insulation requirements:

"All supply and return air ducts and plenum shall be insulated with a minimum of R-5 insulation when located in conditioned spaces and with a minimum of R-8 insulation when located outside the building. When located within a building envelope assembly, the duct or plenum shall be separated from the building exterior or unconditioned or exempt space by a minimum of R-8 insulation. Exceptions: 1. When located within equipment. 2. When design temperature differential between the interior and exterior of the duct or plenum does not exceed 15˚F (8˚C)".