The International Code Council (ICC) and International Association of Plumbing and Mechanical Officials (IAPMO) both promulgate mechanical codes that have required residential load calculations for years. Manual J is the only ANSI-recognized consensus standard for residential load calcs, and is referenced specifically by both code organizations. This portion of the presentation will review the specific code requirements in the International Residential Code (IRC) and the Uniform Mechanical Code (UMC), and then go on to explain the CLTD method for residential load calculations contained in Manual J.