Much of the energy usage in a commercial building can be attributed to systems that are operating under the assumption that the building is “occupied.” Generally in an occupied mode, the lights are on, HVAC systems are operating, and we are delivering code-required ventilation, as well as occupied heating and cooling setpoints.
On many sites, occupancy is determined through a schedule that often starts early in the morning (in anticipation of the first occupants’ arrival) and runs until late at night after the last occupants (often a cleaning crew) are gone. We know though that these assumptions about occupancy are flawed. The actual building occupancy hours may be much shorter than how the schedule is set up, and even during these hours, not all spaces are fully occupied at all times. The end result is often that we are conditioning space for many more hours than is required, resulting in significant energy waste.