Assists code users in understanding the principles on which the 2018 IgCC is based, the requirements of the IgCC, and how those requirements may be met. The Manual was developed to improve the ability of these users to understand the IgCC by providing explanations of the its requirements and examples of its application. This publication contains sample calculations, forms to demonstrate compliance, and references to helpful resources and websites. It can also be suitable for use in educational programs. The Manual is intended to aid many building professionals, including architects, engineers, and other design professionals applying the IgCC to the design of their buildings; general and specialty contractors constructing buildings in compliance with the IgCC; plan examiners, field inspectors, and other code officials enforcing the IgCC in areas where it is adopted as code; and product manufacturers, state and local energy offices, policy groups, and others.