Reducing Utility Costs of Ventilation Air

Ventilation load can be a significant portion of a building’s heating and cooling load and subsequently a building’s utility costs. Finding ways to reduce the energy use associated with ventilation load can greatly reduce these costs. Two methods of reducing these energy costs are to utilize energy recovery ventilation equipment or demand control ventilation.

Energy recovery ventilation (ERV) is the process of exchanging the energy contained in the exhaust from a building and using it to treat (pre-condition) the incoming outdoor ventilation air. During the warmer seasons, the system pre-cools the incoming air, while in the cooler seasons it pre-heats the incoming air. Depending on the type of recovery system used, the system can also dehumidify while it pre-cools and humidify while it pre-heats the ventilation air.

Demand Controlled Ventilation (DCV) is the automatic adjustment of ventilation equipment according to occupant use in a space. DCV is a control method that modulates the amount of ventilation air into an enclosed space or building by mechanical air conditioning equipment. Commonly, demand control is achieved by measuring the indoor and outdoor carbon dioxide (CO2) levels to estimate the number of people in a space, since humans give off CO2.

Determining which method to utilize to help reduce a building or spaces energy use is dependent on the space occupancy, space occupancy variability, and the building systems. Spaces with a highly variable occupancy, such as an auditorium or gymnasium, can have more benefit from a demand control ventilation system. Spaces that have a more consistent occupancy, such as a classroom, may have more benefit utilizing energy recovery ventilation.

If you think your current building or a future building project would benefit from these design strategies, or if you would like assistance with an upcoming project, please contact Michael E. Shafer, PE at or (717) 845-7654.