Most buildings are commissioned when they are first built. Retrocommissioning (RCx) happens later in a building's life. It is a one-time process intended to restore buildings to their optimal performance capabilities. Existing buildings can undergo retrocommissioning whether or not they were originally commissioned. Buildings must first be commissioned before they can take part in ongoing commissioning. This way, baseline usage can be documented for later comparison.
By identifying and improving problem areas, RCx can reduce operating costs such as repairs and replacements. The aim of RCx is to fine-tune existing equipment and perform preventative maintenance on heating, cooling and lighting systems so that large-ticket replacements can be avoided.
Image credit: Energy Star retrocommissioning manual