TABLE 12
LUMINAIRE MAINTENANCE CATEGORIESPROCEDURE FOR DETERMINING LUMINAIRE MAINTENANCE CATEGORIES
To assist in determining luminaire dirt depreciation (LDD) factors, luminaires are separated into six maintenance
categories (I through VI). To arrive at categories, luminaires are arbitrarily divided into sections—atop enclosureand a
bottom enclosure—by drawing a horizontal line through the light center of the lamp or lamps. The characteristics
listed for the enclosures are then selected as best describing the luminaire. Only one characteristic for the top
enclosure and one for the bottom enclosure are used in determining the category of a luminaire. Percentage of
uplight is based on 100% light output for the luminaire. The maintenance category is determined by the
characteristics in both enclosure columns. If a luminaire falls into more than one category, the lower-numbered
category is used.Maintenance Category Top Enclosure Bottom Enclosure
I 1. None 1. None
II 1. None 1. None- Transparent with 15% or more uplight
through apertures
2. Louvers or baffles - Translucent with 15% or more uplight
through apertures - Opaque with 15% or more uplight
through apertures
III 1. Transparent with less than 15% upward
light through apertures - None
- Translucent with less than 15% upward
light through apertures
2. Louvers or baffles - Opaque with less than 15% upward
light through apertures
IV 1. Transparent unapertured 1. None - Translucent unapertured 2. Louvers or baffles
- Opaque unapertured
V 1. Transparent unapertured 1. Transparent unapertured - Translucent unapertured 2. Translucent unapertured
- Opaque unapertured
VI 1. None 1. Transparent unapertured - Transparent unapertured 2. Translucent unapertured
- Translucent unapertured 3. Opaque unapertured
- Opaque unapertured
Reprinted from theIES Lighting Handbook, 9thEd. Used with permission from the Illuminating Engineering Society of
North America.
INTERIOR LIGHTING FOR DESIGNERS