This training explores how to determine accurate heating and cooling loads for homes and explains why they are critical for right-sizing, comfort, efficiency, and code or program compliance. Key topics include an overview of Manual J, S, and D, covering the roles of Manual J (room-by-room and whole-house loads), Manual S (equipment selection), and Manual D (duct design) and how they interconnect. The session also highlights critical details for accurate load calculations, such as design temperatures, envelope U/R values, orientation and shading, infiltration and ventilation, internal gains, duct location and leakage, setpoints, and data sources. Additional focus is placed on defining sensible and latent loads, distinguishing between load and equipment capacity, and understanding their impacts on comfort, efficiency, reliability, and costs. Live load calculation demonstration examples are also included.