Maximum Luminances and Luminance Ratios and their Impact on Users' Discomfort Glare Perception and Productivity in Daylit Offices: Testing the Hypothesis: Maximum Luminance and Ratio Recommendations For Visual Comfort Should be Specific to the Luminous
Authors:   , Linney Andrew Scott 
Published: November 2021

<p>Lighting is an important environmental factor when considering health and safety, visual comfort and workplace design. But how well do we really understand the implications of lighting on these factors, especially in a workplace environment? When one attempts to digest the enormous volume of information of the past century regarding recommended lighting conditions, one begins to see that these recommendations are varied, not extensively tested and often apply to a very limited set of luminous conditions. In a world with daylighting design which increasingly challenges creative and technological boundaries, it is important that the factors and limits which contribute to visual comfort are well understood in order to test these new designs. Daylighting design also becomes important simply from a sustainability standpoint with energy efficiency becoming increasingly important in this age of diminishing natural resources. With an increase in the amount of daylight in buildings spawning from this desire to capitalize on the free and daily renewable light from the sun, difficult and often immeasurable factors such as a view of the outdoors and higher adaptation levels of space users' eyes could very realistically affect the current limits of the human visual system for visual comfort. Visual comfort, limits, which at best are ball park figures, loosely understood and rarely adhered to. This paper documents the testing of 48 test subjects, all of an age where they could feasibly be expected to work in an office environment, in a simulated contemporary office environment with a simulated daylighting window where the luminous conditions and layout were altered to assess the impact of such changes on visual comfort, productivity and different types of user characteristics. The window is designed so luminances of the window can be changed at will. By comparing subjective assessments of the lighting conditions with test performances, a greater understanding of the luminance limits (maximums and ratios) of the human eye for different contemporary lighting layouts within working-aged populations can be defined. With improved understanding of human tolerances to luminance distributions and lighting conditions which romote visual comfort and productivity, designers can begin to give glare prediction with respect to likely effects on these factors. This information would be highly valuable to office based firms who are currently building new or retrofitting premises (to the point where they would likely pay for it as an investment for future efficiency of their firms) thereby proving beneficial to demand for skilled architects, interior and lighting designers. In comparison to the relatively more complicated glare prediction indices involving various factors and calculations, luminance ratio recommendations are an easy to understand tool which with further study could become a powerful method of site and even user-specific glare prediction in the future.</p>