Impact of different building ventilation modes on occupant expectations of the main IEQ factors

This study explores the relationship between the perceived performance of specific IEQ factors and occupants' overall satisfaction with their workspace. In particular we examine the influence of ventilation system type (i.e. Air-Conditioned AC, Mixed-Mode MM, Naturally Ventilated NV) on that relationship. Statistical analyses were conducted on the post-occupancy survey database from the University of California at Berkeley's Center for Built Environment (CBE) to estimate the relative importance of individual IEQ factors on occupants' overall satisfaction, depending on whether or not the occupants were satisfied with the IEQ factor in question. Based on these analyses, 15 IEQ factors were classified as Basic Factors, Bonus Factors or Proportional Factors, according to their relationship with overall satisfaction, as described in Kano's satisfaction model. We found that the classification of some IEQ factors differed for the occupants of AC, MM and NV buildings, suggesting that occupants of buildings with different ventilation types have different expectations, and respond in different ways to various aspects of the indoor environment. A noticeable difference was in thermal environmental conditions: in NV buildings, good thermal conditions were associated with significantly enhanced overall satisfaction (i.e. strong positive impact), but there was little discernible adverse impact, even when thermal performance was deemed to be poor. In AC buildings, on the other hand, thermal conditions were more directly associated with negative overall evaluations of workspace by occupants (i.e. greater negative impact than positive impact). Finally, in MM buildings, thermal conditions exerted both positive and negative impacts of comparable intensities on overall satisfaction.