Evaluating the influence of personal control in allowing building occupants to be comfortable in a wider range of conditions than prescribed by existing standards.
Status: Completed
Funding Sources: CBE Industry Consortium ASHRAE 1161
Project Objective
Determine how the use of operable windows in office buildings affects occupants’ thermal comfort and acceptance of variable thermal environments. Previous work developing the adaptive model of thermal comfort showed that occupants prefer a wider range of temperatures than in sealed buildings. This project investigated the extent to which this difference is related to the amount of control that occupants have over their environment.
Project Results
Our findings offer strong empirical confirmation for the role of shifting expectations in the adaptive model of thermal comfort. We found that occupants experienced similar thermal environments, independent of proximity to and level of control over operable windows. Despite the similarity of conditions, the reactions of the high and low personal control groups were significantly different. Occupants who had greater control preferred a wider range of temperatures. These findings reinforce the adaptive comfort model.
Significance to Industry
Thermal environments in buildings with operable windows are typically more variable and less predictable than those in fully air-conditioned buildings. In naturally ventilated buildings, occupants prefer a wider range of temperatures than in sealed buildings. If this is because of increased personal control, it may be more appropriate for standards such as ASHRAE 55 to segregate their requirements based on the level of occupant control instead of simply the type of ventilation. This would save energy by allowing the adaptive comfort standard to apply to many mixed-mode buildings.
Research Approach
We conducted a field study to quantify the degree to which personal control of operable windows influences local thermal conditions and occupant response. Test methods included physical measurements and online occupant questionnaires that addressed personal control of operable windows, thermal variability, comfort, and window use patterns.
Utilizing continuous measurement of each subject’s workstation microclimate, plus a Web-based survey that subjects took several times a day and was cross-linked to concurrent physical assessments of workstation microclimatic conditions, we collected over 1000 survey responses in each of the two main seasons.
Publications and Reports
Brager, G.S., G. Paliaga, and R. de Dear, 2004. Operable Windows, Personal Control and Occupant Comfort. ASHRAE Transactions, 110 (2), June.