The ventilation airstream required to maintain acceptable indoor air quality is typically a significant contributor to the total heating and cooling load in commercial buildings. Demand-controlled ventilation (DCV) and enthalpy exchangers are two technologies that can be used to reduce ventilation loads and overall operating costs. This paper evaluates the operating cost savings and overall economics associated with these two different ventilation load reduction technologies for a variety of small commercial building types and climates. A specialized simulation tool was developed and utilized to perform the evaluations. Both demand-controlled ventilation and enthalpy exchangers were shown to result in significant operational cost savings as compared with fixed ventilation and no energy recovery in a number of small commercial buildings and locations. For both technologies, the savings potential and economic payback are better in more extreme climates. The opportunities are particularly great in cold climates because the ventilation load is a larger portion of the overall load. For retrofit applications, demand-controlled ventilation (DCV) with an economizer was found to give the greatest savings in utility costs for all the buildings and climates considered. Air-conditioning utility cost savings for DCV of up to 52% were found for offices and restaurants. Payback ranged from about one to six years for most locations. Although utility cost savings were found to be less for enthalpy exchangers, they have the advantages of allowing smaller primary cooling and heating equipment for new applications and providing better indoor air quality. The operating cost savings for both DCV and enthalpy exchangers are dependent on assumptions concerning occupancy. The impact of occupancy schedules on cost savings for DCV and enthalpy exchanger systems should be considered in more detail in future studies.

Units: Dual