Critical factors and thresholds for user satisfaction on air quality in office environments

Indoor Air Quality (IAQ) of the workplace is highly linked with occupants' health, comfort and satisfaction. To maintain the good IAQ of buildings, Post-Occupancy Evaluation (POE) is often combined with environmental measurements to holistically examine existing performance conditions in relation to occupants’ satisfaction. The Center for Building Performance and Diagnostics (CPBD) at Carnegie Mellon University conducted post occupancy evaluations for over 1600 workstations in 64 buildings using the National Environment Assessment Toolkit (NEAT)—a suite of three tools for workstation IEQ measurements, Technical Attributes of Building Systems (TABS) and occupant satisfaction surveys. The rich dataset generated by NEAT was employed in this study to perform multivariate regression and multiple correlation coefficient analyses on IAQ. We examine the relationship between measured and perceived IAQ indices, as well as interdependencies between IAQ indices and occupant satisfaction variables of significance. Among measured IAQ indices, CO₂ and particulates are identified as critical factors for user satisfaction. In particular, the analyses revealed that the CO₂ threshold of 582 ppm is the highest occupant satisfaction in office buildings. To ensure good air quality in office buildings, our findings recommend “Operable window”, “Dedicated exhaust”, “Individual return air diffuser density” and “Low/medium partition height” as applicable design guidelines. Through this study, we demonstrate the effectiveness of integrating POE with environmental measurements to systematically develop a rich database leading to critical thresholds and design guidelines for highest occupant satisfaction.