Center for the Built Environment

Commercial office buildings promoted as “sustainable,” “energy efficient,” “green,” or“high performance” often reference use of daylight as a key strategy for reducing energyconsumption and enhancing indoor environmental quality. However, buildings are rarelystudied in use to examine if the design intent of a sufficiently daylit and a visuallycomfortable work environment is achieved from the perspective of building occupants orhow occupant use of shading devices may affect electrical lighting energy reduction fromphotocontrols. This dissertation develops a field-based approach to daylightingperformance assessment that pairs repeated measures of occupant subjective responseusing a novel desktop polling station device with measurements of the physicalenvironment acquired using High Dynamic Range (HDR) imaging and otherenvironmental sensors with the objective of understanding the physical environmentalconditions acceptable to occupants. The approach is demonstrated with a 6-month fieldstudy involving (N=44) occupants located in perimeter and core open-plan office spacesin the San Francisco Federal Building1 (SFFB). Over 23,100 subjective assessmentspaired with physical measures were analyzed to develop models of visual discomfort andshade control and to examine the assumptions of existing daylighting performanceindicators. The analysis found that existing daylight performance indicatorsoverestimated the levels of daylight illuminance required by occupants to workcomfortably without overhead ambient electrical lighting. Time-lapse observation ofinterior roller shades showed that existing shade control models overestimated thefrequency of shade operation and underestimated the level of facade occlusion due tointerior shades. Comparison of measured results to the daylighting objectives of theSFFB showed that available daylight enabled electrical lighting energy reduction in theperimeter zones but not in the open-plan core zones. The results extend existingknowledge regarding the amount of daylight illuminance acceptable for occupants towork comfortably without overhead electrical lighting and for the physical variables (andstimulus intensities) associated with visual discomfort and the operation of interiorshading devices.