From early in the last century there existed three major code authorities, each of which had established and was maintaining its own set of model building codes in different parts of the United States. These three authorities were:

• Building Officials and Code Administrators International (BOCA)
• International Conference of Building Officials (ICBO)
• Southern Building Code Congress International (SBCCI)

In 1994, recognizing the need for a single set of codes without regional limitations, these three groups established The International Code Council (ICC). Its mission: "To promulgate a comprehensive and compatible regulatory system for the built environment, through consistent performance-based regulations that are effective, efficient and meet government, industry and public needs."

While the ordinances of some local jurisdictions may still reference BOCA, ICBO, and SBCCI codes, nation-wide acceptance of the ICC set of codes is fast becoming a reality, This makes it possible for architects, engineers, manufacturers of building materials and systems, contractors, and code enforcement officials to work with the same regulatory system anywhere in the United States.

It should be noted that some states have established their own building, energy or environmental codes, and that these codes do not necessarily relate to the ICC set of codes. Some state codes may be more or less stringent than the ICC codes.

Among the codes developed by ICC, the following most directly relate to HVAC duct systems in commercial construction:

• International Mechanical Code
• International Energy Conservation Code

These codes supersede:

• BOCA National Code, 1996 Edition and National Mechanical Code, 1996 Edition
• ICBO Uniform Building Code, 1997 Edition and Uniform Mechanical Code, 1997 Edition
• SBCCI Standard Building Code, 1997 Edition and Standard Mechanical Code, 1997 Edition
• CABO (Council of American Building Officials) Model Energy Code, 1997 Edition

ICC codes relating to HVAC duct systems in residential or light commercial construction include:

• International Residential Code
• International Energy Conservation Code

These codes supersede:

• CABO One and Two Family Dwelling Code, 1995 Edition

Although these codes also deal with issues such as fire safety, indoor environmental quality, and acoustics (among others), the key concerns relative to HVAC duct system insulation can be summed up as follows:

Mechanical codes answer the question, "What physical properties are required of the insulation?"

Energy codes answer the question, "How much insulation is needed in this particular application?"