A Multi-criteria Daylighting Performance Assessment Method for Cellular Offices

Daylighting design in interiors faces frequent criticism. Limitations of existing indicators to explain the overall indoor daylighting performance were blamed. This thesis, using local cellular offices as the research target, aims to develop a novel daylighting performance assessment method with a broader insight. It hypothesizes that daylighting performance in a cellular office depends on a series of criteria and decision factors, and every occupant has a similar tendency towards each influential factor. The theory of Analytic Hierarchy Process (AHP) was adopted. A three layer hierarchy was established --- good daylighting performance as a goal to be achieved was at the top, occupants' visual satisfaction and electric lighting energy saving potential supposed to be the two criteria having equal weight of influence to contribute to the goal were in the middle, and the five decision factors which were found statistically correlated with the criteria, i.e. brightness and uniformity on task and surroundings and perceived glare from the side window, were at the bottom. Their individual weights of importance were obtained by AHP pairwise comparisons. User assessment surveys and field measurements with the introduction of High Dynamic Range (HDR) photography were conducted to reveal the correlated lighting parameters. The, probabilities that occupants would feel visually satisfied and accept not turning on electric lights in their sidelit cellular offices were expressed. On the other hand, the hourly probabilities of occurrence of the three typical sky types in this city throughout a year were computed. Twelve different cellular offices were modelled under these sky types by lighting simulation software for their hourly daylighting situations such that the numerical values of the correlated lighting parameters accounting for those decision factors were obtained. The hourly probabilities of achieving good daylighting performance were calculated and transformed to be the multi-criteria daylighting performance indicator of that hour, which was then named as the Daylighting Performance Index (DPI). This new index considers both human factors and energy issues, and offers a more comprehensive performance-based assessment method for interior daylighting. It is believed that applying the DPI grading scheme introduced in this thesis can accomplish a well-performed daylighting design.