IES METHOD - Table 1

IES ILLUMINANCE CATEGORIES and VALUES - for GENERIC INDOOR ACTIVITIES

ACTIVITY CTGRY LUX FOOTCANDLES

Public Spaces with dark surroundings A 20-30-50 2-3-5

Simple orientation for short temporary visits B 50-75-100 5-7.5-10

Working spaces where visual tasks are only occasionally performed C 100-150-200 10-15-20

Performance of visual tasks of high contrast or large size D 200-300-500 20-30-50

Performance of visual tasks of medium contrast or small size E 500-750-1000 50-75-100

Performance of visual tasks of low contrast or very small size F 1000-1500-2000 100-150-200

Performance of visual tasks of low contrast or very small size over a prolonged period

G 2000-3000-5000 200-300-500

Performance of very prolonged and exacting visual tasks H 5000-7500-10000 500-750-1000

Performance of very special visual tasks of extremely low contrast I 10000-15000-20000 1000-1500-2000

A-C for illuminances over a large area (ie lobby space)D-F for localized tasksG-I for extremely difficult visual tasks

Table - 1a - (for Categories A-C)

Room and Occupant Characteristics Weighting Factor

-1 0 +1

Occupant ages under 40 40-55 over 55

Average room surface reflectances more than 70% 30-70% less than 30%

Table - 1b - (for Categories D-I)

Room and Occupant Characteristics Weighting Factor

-1 0 +1

Occupant ages under 40 40-55 over 55

Importance of speed and/or accuracy not important important critical

Average room surface reflectances more than 70% 30-70% less than 30%

Point Source Method

i =L • cos Θ

r²i = point source illuminanceL = lumensΘ = angle offset from 90°r = distance to surface

Lumen Method

E =n • N • F • UF • LLF

Area

E = average illuminance over the horizontal working planen = number of lamps in each luminaireN = number of luminaireF = lighting design lumens per lamp, i.e. initial bare lamp luminous fluxUF = utilization factor for the horizontal working planeLLF = light loss factor A = area of the horizontal working plane

FC = .0929(LUX)LUX = 10.76 (10.76)50 FC = 538 LUX

FC=Candela

d² (ft.)

LUX=Candela

d² (m)

FC=Lamp Lumens

Area (ft²)

LUX=Lamp Lumens

Area (m²)

M.S. Rae Method - Table 2

TASK CATEGORIES AND REFERENCE ILLUMINANCE LEVELS

CTGRY Difficulty of Visual Task Importance of Speed & Accuracy

non-critical critical

A Movement through public spaces 505

LuxFC

757

B Infrequent Reading or WritingHigh contrast & large size

1009

LuxFC

15014

C Frequent & Easy Reading or WritingHigh contrast & large size

20019

LuxFC

30028

D Moderately Difficult Reading or Writing 30028

LuxFC

45042

E Difficult Reading or Writing 50046

LuxFC

75070

Table 2A

ADJUSTMENTS TO REFERENCE ILLUMINANCES(for different task background reflectances and worker ages)

Age (A, in years)

Task Background Reflectance

(R)

> 30 30-40 40-50 50-60 60+

R > 0.8 1.0 1.2 1.5 2.0 3.1

0.8 - 0.6 1.2 1.5 1.9 2.6 3.9

0.6 - 0.4 1.7 2.0 2.5 3.4 5.2

0.4 - 0.2 2.5 3.0 3.8 5.1 7.8

0.2 or less 5.0 6.0 7.6 10.2 15.6

Utilization Factor Fixture efficiency

Ceiling[%] 70 50 30

Walls[%] 50 30 10 50 30 10 50 30 10

Floor[%] 30 10 30 10 30 10 30 10 30 10 30 10 30 10 30 10 30 10

Room Index

0.60 .27 .26 .22 .22 .19 .19 .26 .24 .22 .21 .19 .18 .26 .25 .21 .21 .19 .18

0.80 .33 .31 .28 .27 .23 .23 .32 .30 .27 .26 .24 .23 .31 .30 .27 .26 .23 .23

1.00 .38 .36 .32 .30 .28 .28 .36 .35 .32 .31 .29 .27 .35 .34 .31 .30 .28 .27

1.25 .43 .40 .37 .35 .33 .32 .41 .39 .36 .35 .33 .32 .39 .37 .35 .34 .32 .31

1.50 .47 .43 .41 .39 .37 .35 .44 .42 .40 .37 .36 .35 .42 .40 .39 .37 .36 .35

2.00 .52 .47 .47 .44 .43 .41 .49 .46 .45 .43 .42 .40 .47 .45 .44 .42 .41 .40

2.50 .58 .50 .51 .47 .48 .44 .53 .49 .49 .46 .46 .44 .50 .48 .47 .45 .45 .43

3.00 .59 .52 .55 .49 .51 .47 .55 .52 .52 .48 .49 .46 .52 .50 .50 .48 .47 .46

4.00 .62 .55 .59 .52 .56 .51 .58 .53 .56 .52 .53 .50 .55 .52 .53 .51 .51 .49

5.00 .64 .56 .62 .55 .59 .53 .60 .55 .58 .53 .56 52 .57 .54 .55 .52 .52 .51

Room Index

k=L+W

Hwp (L+W)

white, off-white, gray, lights tints of blue or brown 75-90%

medium green, yellow, brown or gray 30-60%

dark gray, medium blue 10-20%

dark blue, brown, dark green, and many wood finishes 5-10%

white acoustical tile ceiling 70-80%

carpeting 15-30%

high quality white paint or reflective aluminum 90-95