Retro-commissioning, or building energy optimization, is a process that seeks to improve how building equipment and systems function together. Like any complex system, buildings lose their operating efficiency over time and need a “tune up” to help re-align factory settings, or in many situations, correct settings for energy optimization. Retro-commissioning can often resolve problems that occurred during design or construction, or address problems that have developed throughout the building’s life. Once an investigation is conducted, calculations can be made to determine how to optimally configure building optimization using low cost measures.