Daylighting

Designing buildings so natural light does the work of lighting the space.

Quick Answer

Daylighting is the deliberate use of natural light to illuminate building interiors. Designers shape windows, skylights, light shelves, and room geometry to bring in useful daylight while limiting glare and heat gain. Done well, it reduces electric lighting use and improves occupant comfort, and it is evaluated with simulation metrics such as sDA and ASE.

The Full Picture

Daylighting is a design strategy, not just a window count. The goal is to deliver enough natural light where people work and live, evenly enough to be comfortable, without causing glare, overheating, or fading of finishes. Orientation, window placement and size, glazing properties, shading, and interior surface reflectance all play a part.

Common strategies include sidelighting through windows, toplighting through skylights and roof monitors, light shelves that bounce light deeper into a room, and light-colored ceilings and walls that spread it. Shallow floor plates, atria, and clerestory windows can bring daylight to spaces that would otherwise sit in the dark.

Designers evaluate daylighting with simulation. Widely used annual metrics include spatial daylight autonomy (sDA), the share of floor area receiving a target illuminance for a set share of occupied hours, and annual sunlight exposure (ASE), which flags areas at risk of excessive direct sun. Both are defined in the Illuminating Engineering Society's LM-83 method and are referenced by green building rating systems such as LEED.

Daylighting involves tradeoffs. More glass can bring more light but also more heat gain, heat loss, and glare, so it is usually balanced against energy modeling and visual comfort analysis. Automatic lighting controls that dim electric lights when daylight is available are what turn good daylight into measurable energy savings.

Real Examples

→Classroom design: A school orients classrooms to the north and south with clerestory windows and light shelves, giving even daylight across the room and letting the electric lights dim most of the day.

→Deep office floor: A designer adds a central atrium and lighter interior finishes so spaces far from the facade still receive usable daylight.

→Glare control: A simulation shows a west-facing conference room exceeds sunlight exposure limits, so the team adds exterior shading and a lower-transmittance glass.

Common Misconceptions

People assume: More windows always means better daylighting.

Actually: Excess glazing can cause glare, overheating, and higher energy use. Good daylighting balances light quantity, distribution, and solar control.

People assume: Daylighting saves energy automatically.

Actually: Savings depend on lighting controls that dim or switch off electric lights in response to daylight. Without them, the lights often stay on at full output.

Frequently Asked Questions

What is daylight autonomy?

Daylight autonomy measures the percentage of occupied hours that a point in a space receives at least a target level of illuminance from daylight alone. Spatial daylight autonomy (sDA) reports the share of floor area that meets the target.

What is annual sunlight exposure (ASE)?

ASE is the share of floor area that receives direct sunlight above a high illuminance threshold for many hours a year. It flags places likely to suffer glare or overheating.

How does daylighting relate to LEED?

LEED includes daylight credits that use simulation metrics such as sDA and ASE, or in some cases measurement and prescriptive paths, to reward designs that provide good daylight.

Does daylighting affect heating and cooling?

Yes. Glazing that admits light also admits or loses heat, so designers balance daylighting against energy performance, often by using energy modeling alongside daylight simulation.