This module covers the principles and execution of Functional Performance Testing (FPT) and the use of trend data to verify system operation. Participants will learn how functional testing is used to confirm that building systems operate in accordance with the sequence of operations and design intent. The course explains how to develop functional test procedures, use short‑term and long‑term trends, and apply truth tables and manual observations during testing. In addition, the module introduces best practices for reviewing and analyzing trends to identify scheduling issues, control deficiencies, airflow and pressure problems, economizer performance issues, and opportunities for system optimization during commissioning and Retro‑Commissioning projects.