What Is Natural Lighting and Daylighting?
Daylighting is the practice of designing windows, skylights and interior layouts to bring natural light deep into a building, reducing electric lighting use while improving occupant well-being. It's measured using the Daylight Factor, which compares indoor to outdoor illuminance.
Daylighting uses windows, skylights, light shelves and reflective surfaces to distribute natural light throughout interior spaces; performance is quantified by the Daylight Factor: DF = (Ei / Eo) × 100.
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Step-by-step worked examples
A room has an interior illuminance of 500 lux while the exterior illuminance under an overcast sky is 10,000 lux. Find the Daylight Factor.
DF = (Ei / Eo) × 100 DF = (500 / 10,000) × 100 DF = 5%
A deep classroom measures 150 lux at the back wall when the exterior illuminance is 15,000 lux. Find the Daylight Factor at that point.
DF = (150 / 15,000) × 100 DF = 1%
A well-daylit office near a window reads 900 lux interior with 12,000 lux exterior. How does its Daylight Factor compare to a minimum recommended DF of 2%?
DF = (900 / 12,000) × 100 = 7.5% 7.5% is well above the 2% minimum recommended for adequate daylighting
Flashcards
Quick quiz
Q1.What does the Daylight Factor formula DF = (Ei/Eo) × 100 measure?
Q2.Interior illuminance is 400 lux, exterior is 20,000 lux. What is the Daylight Factor?
Q3.As distance from a window increases, Daylight Factor typically:
Q4.What device redirects daylight deeper into a room while shading the area below?
The full card deck, worked steps and AI-tutor support for “What Is Natural Lighting and Daylighting?” are in Notek — study by hand before your exam.
Common mistakes
More windows always mean better daylighting. — Correct: Oversized, unshaded windows can cause glare and overheating; well-placed, properly sized windows with shading perform better.
Daylight Factor depends on the time of day and weather. — Correct: DF is a fixed ratio calculated under standardized overcast-sky conditions, independent of sun position or time.
Daylighting only matters near the building perimeter. — Correct: Skylights, light shelves, and interior glazing can bring daylight into deep floor plates and core spaces too.
Higher Daylight Factor is always better. — Correct: Excessively high DF (bright, unshaded spaces) can cause glare and overheating; there's an optimal comfortable range.
FAQ
What is daylighting in architecture?
Daylighting is designing windows, skylights, and interior layouts to bring natural light deep into a building, reducing electric lighting energy use and improving occupant well-being.
What is the Daylight Factor formula?
DF = (Ei / Eo) × 100, where Ei is interior illuminance and Eo is exterior illuminance under an overcast sky, both measured in lux.
What are examples of daylighting strategies?
Skylights, clerestory windows, light shelves, light wells, glazed interior partitions, and reflective ceiling/wall finishes.
How do you calculate the Daylight Factor?
Divide the interior illuminance (lux) by the simultaneous exterior illuminance (lux) under an overcast sky, then multiply by 100 to get a percentage.