Building envelope impact on human performance and well-being: experimental study on view clarity

The goal of this project was to assess the visual effect of selected aspects of the building envelope on human performance and perception, first broadly, and then focused on view clarity. The initial literature review examined human factors that could be explicitly considered in building envelope design, operation and current daylight metrics. We found that debate remains on the practical applicability of these metrics, and gaps exist between daylight and other building envelope-related aspects such as view. Following the literature review, we narrowed down our research question to experimentally investigate the visual performance of fabric shading systems and electrochromic windows under both diffuse and direct sunlight conditions, and develop a view clarity rating method. We introduce and show results from an experimental study done at Lawrence Berkeley National Laboratory’s Windows Testbeds. We tested High Dynamic Range (HDR) photography techniques to capture the different view clarity through the selected building envelope layers (shades and electrochromic glass) under various sky conditions. The experimental study reveals that light fabric shades restrict the view compared to dark fabric shades, and that view clarity through a blind can be significantly reduced when there is direct sun in the field of view (at certain sun angles). The direct sun caused white-spotted visual noise at the partial area of the fabric shade. Hence, the view was more obscured by the effect of the direct sun even though in this case there was a greater vertical illuminance than the others. The study also shows the potential of HDR photography techniques to be used for a standard view clarity rating method, while noting that further support is needed from human subject testing and advanced computational image analysis algorithms