This is a legacy version of the WELL Building Standard. Please check the latest version here.

Daylighting fenestration

Exposure to natural light can improve mood, alertness and overall health. Ideal lighting begins with proper exposure to diffuse daylight as well as careful design of windows and glazing to avoid excessive glare and heat gain. Balancing energy performance, thermal comfort and access to quality daylight are essential to proper building design.

This feature outlines design parameters for windows to optimize the quantity and quality of daylight.

Part 1: Visual Acuity for Working and Adult Education

The ambient lighting system at workstations is:

a. Able to maintain an average light intensity of 215 lux [20 fc] or more, measured on the horizontal plane, 0.76 m [30 inches] above finished floor. The lights may be dimmed in the presence of daylight, but they are able to independently achieve these levels.
b. Zoned in independently controlled banks no larger than 46.5 m_ [500 ft²] or 20% of open floor area of the room (whichever is larger).
Part 2: Window Transmittance in Working and Learning Areas

The following visible transmittance (VT) conditions are met for all non-decorative glazing:

a. All glazing located above 7 feet from the floor (Daylight Glass) has VT of 60% or more.
b. All glazing located below 7 feet from the floor (Vision Glass) has VT of 50% or more.
Part 3: Uniform Color Transmittance

All windows used for daylighting meet the following requirement:

a. Windows have uniform color transmittance so as not to transmit color-tinted light.
Part 4: Window Sizes for Living Spaces

Window/wall ratio as measured on external elevations is:

a. Between 30% and 60% in living rooms.
b. Between 20% and 40% in bedrooms.
Muscular
Nervous
Reproductive
Cardiovascular
Digestive
Endocrine
Lymphatic
Immune

Applicability Matrix

Core & Shell Tenant Improvement New Construction
Part 1: Visual Acuity for Working and Adult Education - P P
Part 2: Window Transmittance in Working and Learning Areas O O O
Part 3: Uniform Color Transmittance O O O
Part 4: Window Sizes for Living Spaces - - -
Commercial Kitchen Schools Multifamily Residential Restaurant Retail
Part 1: Visual Acuity for Working and Adult Education - P - - -
Part 2: Window Transmittance in Working and Learning Areas O O - O O
Part 3: Uniform Color Transmittance O O O O O
Part 4: Window Sizes for Living Spaces - - O - -

Verification Methods Matrix

Letters of Assurance Annotated Documents On-Site Checks
PART 1 (Design)
Visual Acuity for Working and Adult Education
Architect Spot Measurement
PART 2 (Design)
Window Transmittance in Working and Learning Areas
Architect
PART 3 (Design)
Uniform Color Transmittance
Architect
PART 4 (Design)
Window Sizes for Living Spaces
Architect