Empirical Predictive Modeling of the Impact of Ventilation and Filtration on Energy Cost and Monetized IAQ Exposure in Offices in the U.S

Organizations set minimum ventilation standards in order to maintain acceptable indoor air quality (IAQ) in indoor environments. For example, the American Society of Heating, Refrigeration, and Air Conditioning Engineering (ASHRAE) calls for a minimum ventilation rate (VR) of 8.5 l/s-occ at standard occupant density (5 occupants per 100m²) in offices. However, new studies have shown that higher VRs in offices can have positive effects on occupants’ wellbeing, including increased productivity and fewer incidences of absenteeism and sick building syndrome. These positive effects come at a cost associated with increased energy consumption due to additional outdoor air that needs to be conditioned, as well as greater introduction of outdoor-originating to the indoors, namely particulate matter (PM), which can degrade the health of the occupants. This study used a detailed outcome simulation of a typical office environment using EnergyPlus in conjunction with outdoor pollutant data collected by the U.S. Environmental Protection Agency (USEPA) to model the energy consumption and exposure to pollutants with outdoors sources (CO, O₃, NO₂, and PM_2.5) in the indoor environment under various constant VRs (0, 8,5, 17, and 25.5 l/s-occ). The simulation also considered seven filters of different minimum efficiency reporting values (MERVs) to assess their effects on occupant exposure to indoor PM concentrations. The intake-incidence-DALY (IND) method was used to estimate the disability-adjusted life years (DALYs) lost due to the occupants’ exposure to these outdoor originating pollutants. The energy consumption and DALYs lost due to exposure were monetized and their trends were assessed to create a unique empirical function that can predict the likely total cost associated with increased ventilation. This function can be used to estimate a building’s performance under any combination of constant ventilation and filtration within our studied range, so the cost associated with ventilating at high VRs may be easily compared with its many benefits on occupant wellbeing.