What Is Daylighting in Sustainable Building Design?
Daylighting is the deliberate use of natural light to illuminate interiors — window placement, skylights, light shelves, and atria designed so electric lights can dim or switch off during the day. It cuts lighting energy (historically 20-30% of commercial building energy), improves occupant well-being and productivity, and earns LEED and energy code credits. The engineering challenge is harvesting the light without the heat and glare.
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Design strategies
South-facing glazing with light shelves bounces light deep into the space; north glazing gives diffuse glare-free light; skylights and tubular daylighting devices serve interior zones. The architect and lighting designer model daylight autonomy (the percentage of occupied hours lit by daylight alone) — 50%+ is a strong target. Automated shades and photosensor dimming controls are what convert the daylight into actual energy savings.
The heat and glare problem
Every daylighting aperture is also a solar heat gain and glare source. High-performance glazing (low SHGC, high visible transmittance), exterior shading, and electrochromic glass manage the trade-off. The energy modeler proves the net benefit — badly designed daylighting increases cooling loads more than it saves lighting energy. This is an integrated design problem, not a window schedule.
Codes and credits
ASHRAE 90.1 and Title 24 require daylighting controls (photosensors, multilevel switching) in daylit zones — the controls are mandatory even where the daylighting design is voluntary. LEED awards credits for daylight quantity and quality (spatial daylight autonomy, annual sunlight exposure). The MEP engineer designs the control sequences that make the whole strategy actually perform.
The bottom line
Daylighting harvests natural light to cut lighting energy 20-30% — but only with glare/heat control and photosensor dimming. Model it, shade it, and commission the controls.
Torch Engineering PLLC · (480) 490-0064 · info@torchengineering.com — PE stamping backed by Apex Grid Engineering.