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

Electric light glare control

Non-diffuse, bright indoor lights create uneven levels of brightness in the visual field. The resulting glare, defined as “excessive brightness of the light-source, excessive brightness-contrasts and excessive quantity of light”, can cause visual discomfort (discomfort glare), fatigue, visual impairment and even injury (disability glare), and can be attributed to either direct or reflected glare. In the case of glare caused by electric light sources, lamps should be shielded based on their luminance. This quantity, often given in cd/m², can be measured directly or calculated from lighting specification sheets with sufficient detail. Light fixtures of greater luminous intensity require a greater shielding angle to reduce the likelihood of creating direct glare for occupants.

Part 1: Lamp Shielding

The following shielding angles (⍺ = 90 - cutoff angle) must be observed for lamps in regularly occupied spaces with luminance values in the ranges specified:

a. No shielding required for less than 20,000 cd/m² (including reflected sources).
b.79 ⍺: 15° for 20,000 to 50,000 cd/m².
c.79 ⍺: 20° for 50,000 to 500,000 cd/m².
d.79 ⍺: 30° for 500,000 cd/m² and above.
Part 2: Glare Minimization

At workstations, desks, and other seating areas, the following requirement is met:

a.174 Luminaires more than 53° above the center of view (degrees above horizontal) have luminances less than 8,000 cd/m².
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Applicability Matrix

Core & Shell New & Existing Buildings New & Existing Interiors
Part 1: Lamp Shielding - P P
Part 2: Glare Minimization P P P
Commercial Kitchen Education Multifamily Residential Restaurant Retail
Part 1: Lamp Shielding P P P P O
Part 2: Glare Minimization P P P P O

Verification Methods Matrix

Letters of Assurance Annotated Documents On-Site Checks
Part 1: Lamp Shielding Architect
Part 2: Glare Minimization Architect
79

licht.de. licht.wissen 04: Office Lighting: Motivating and Efficient. Frankfurt; 2014: 35.

55.1.b

Office Lighting: Motivating and Efficient notes that to avoid glare caused by bright light sources, lamps should be shielded. The minimum shielding angle for lamp luminance of 20,000 - 50,000 cd/m² is 15°.

55.1.c

Office Lighting: Motivating and Efficient notes that to avoid glare caused by bright light sources, lamps should be shielded. The minimum shielding angle for lamp luminance of 50,000 - 500,000 cd/m² is 20°.

55.1.d

Office Lighting: Motivating and Efficient notes that to avoid glare caused by bright light sources, lamps should be shielded. The minimum shielding angle for lamp luminance of 500,000 cd/m² and above is 30°.

174

American National Standards Institute and Illuminating Engineering Society of North America. American National Standard Practice for Office Lighting. New York, NY: Illuminating Engineering Society of North America; 2012. RP-1-12.

55.2.a

ANSI/IES American National Standard Practice for Office Lighting (RP-1-12) notes that luminaires at angles higher than 53° above horizontal may cause discomfort, and that such luminaires should be less than 8,000 cd/m².