Optimizing Daylighting Performance: Considerations to Maximize Daylighting for Health, Efficiency and Sustainability

Overview

Published by Buildings magazine on November 19, 2025, this five-minute-read article by Neall Digert of Kingspan Light + Air starts from the premise that too little daylight measurably harms occupants and then asks the practical question: what does a design team actually have to consider to get abundant, full-spectrum daylight into a building? It is organized as a checklist across interior criteria, codes and standards, site conditions and product choices, and closes with the health and energy arguments.

Key Findings

• Restricted daylight lowers the brain's serotonin output, contributing to low mood, fatigue and reduced productivity; the author notes the effect becomes acute when Daylight Saving Time ends and evening light disappears.
• Interior factors decide how far daylight travels: open plans, atriums and clerestories carry light deeper; rooms that are too deep for their window height end up underlit; light-colored walls, ceilings and floors bounce more of it around. Where windows are impossible, tubular daylighting devices and skylights are the fallback.
• The Illuminating Engineering Society recommends roughly 300 lux (30 footcandles) for most commercial and institutional spaces and 500 lux (50 footcandles) or more for critical visual tasks such as manufacturing. LEED and WELL use spatial daylight autonomy and annual sunlight exposure as their daylight metrics.
• Site matters: east- and west-facing facades take morning and evening glare, neighboring buildings and trees block or reflect light, and overcast climates should favor diffuse light while sunny ones need shading and glare control.
• Product options include high-performance and low-e glazing, translucent polycarbonate and fiberglass-reinforced polymer panels, light-redirecting systems such as prismatic glazing and light shelves, and skylights and TDDs, which balance perimeter brightness and can light otherwise windowless areas.
• The article cites an Eneref Institute figure of a 40% retail sales increase from well-placed skylights, a Journal of Clinical Sleep Medicine study linking daylight to higher vitality and better sleep, and University College London research tying daylight to reading and science performance.
• The article puts electric lighting at 35% to 50% of a commercial building's annual energy use and says integrated daylighting can cut lighting energy by as much as 50%; it also quotes a market forecast of $401.82 billion by 2028. Those first two figures sit well above the 10% to 20% share that U.S. Energy Information Administration surveys report for commercial lighting, so treat them as the author's framing rather than settled numbers.

Why It Matters for Daylighting

This is essentially a toplighting article written for a general facilities audience. The 500-lux manufacturing target is the level a well-sized prismatic skylight array can meet across a plant floor on most daytime hours, and the author's point about balancing perimeter brightness is the reason skylights outperform wall glazing in deep buildings: light arrives from above, evenly, without the steep fall-off from a window wall. The site-conditions section is a reminder that a skylight-to-floor ratio that works in Seattle will need diffusing glazing and heat-gain control in Phoenix. The 40% retail figure should be treated cautiously; the better-documented Heschong Mahone Group studies found a smaller but statistically significant skylight effect.

About the Source

Buildings is a U.S. trade magazine for commercial building owners and facility managers, published since 1906. Neall Digert, Ph.D., MIES, is vice president of innovation and market development at Solatube International and Kingspan Light + Air North America, a skylight and daylighting manufacturer, so the piece reflects an industry perspective. The library copy is an eight-page printout of the web article. Read the original at buildings.com.