1. Objectives
Finish Lighting system design
Daylighting

2. Illumination Calculation
E = N × F × LLF × LOF × CU / A
E = selected illuminance [fc, lx]
N = number of fixtures
F = installed lumens per fixture [lm]
LLF = Light loss factor
depreciation, position (dust deposit)
LOF = lamp operating factor
Ballast, voltage
CU = coefficient of utilization
Fraction of light that meets the work surface
A = room area [ft2, m2]
N = E  A / (F × LLF × LOF × CU )

3. Zonal Cavity Method
Figure 16-1
Ref: Tao and Janis (2001)

4. Calculate Cavity Ratios
CR = 2.5 × PAR × h
PAR = perimeter to area ratio = P/A
PAR = 2 × (L+ W)/(L × W)
h = height of cavity
What about CR for non-rectangular rooms?
CR = 5 × (L+ W)/(L × W) × h

5. Reflectance Experience Convert to effective reflectance (ρcc, ρw, ρfc)
White ceiling, Rc = 70 – 80 % = ρc
White walls, Rw = % = ρw
Medium to light colored walls, Rw = 50 % =ρw
Dark wood paneling, Rw = 25 % = ρw
Floor, Rf = % = ρf
Convert to effective reflectance (ρcc, ρw, ρfc)
Tables in Tao and Janis (pg , Table 16-6) or from manufacturer

6. Calculation Procedure
Goal is to get CU (how much light from the fixture gets to the work surface)
Data collection
Room geometry
Surface reflectance
Fixture tables
Preliminary calculations
CR for room, floor, and ceiling

7. Calculations (continued)
Table 16.6
ρcc and ρfc (assume ρfc = 20% if no other information given)
Table 16.7
CU Correction if ρfc ≠ 20%
Fixture table (Figure 16-6 page 523, or manufacturer)
CU based on ρcc , ρ w, RCR
Use CU by multiplier from step 4.

8. Example Classroom (30 × 30 × 9)
White ceiling, Medium colored walls, Light floor
Students working on desks
Fluorescent fixtures at ceiling level
Use standard tables

9. Solution PAR = 2 × (L+ W)/(L × W) = 120ft/900ft2
CCR = 2.5 × PAR × hc = 0 (ceiling cavity ration)
RCR = 2.5 × PAR × hr = 2.17 (room CR)
FCR = 2.5 × PAR × hf = 0.83 (floor CR)
Ceiling reflectance 70% (white ceiling)
Wall reflectance 50% (medium colored walls)
Floor reflectance 30% (light color - 30 % is maximum)

10. Solution (continue) Use Table 16-6
Effective ceiling cavity reflectance:
CCR =0, Ceiling reflectance 70% , Wall reflectance 50% → (table) → 70 % (because CCR=0) ρCC= 70%
Effective floor cavity reflectance:
FCR=0.83 (use 2.2) , Floor reflectance 30%, Wall reflectance 50% → (table) → 28% ρFC= 28%
Effective wall cavity reflectance (does not change)
ρW= 50%

11. Solution (continue)
Use Figure 16-6 (page 525)
Luminary 15 is the most similar to the one in classroom:
RCR =2.2, ρCC= 70%, ρW= 50% → (figure) → (interpolation between 52 and 45) CU=51.5%
CU Correction if ρFC ≠ 20% (table 16.7)
ρFC=28 ≈ 30 and ρCC= 70%, ρW= 50%, RCR =2.2 → (table) →
(interpolation between and 1.048) Correction 1.055
CU = 51.5*1.055= 54%=0.54

12. Zonal Cavity Method N = E × A / (F × LLF × LOF × CU)
Instilled lamp lumens per fixture
F=?
Light loss factor
LLF=?
lamp operating factor
LOF=?

13. Lamp operating factor LOF
LOF= VF × BF
VF – Voltage factor
Table 16-4
BF - Ballast factor
Table 16.5

14. Lamp Loss factor LLF LLF= LLD × LDD
LLD – Lamp lumen deprecation (manufacturer or Figure When you use Figure 15-9 use values for 70% of rated lamp life.)
LDD – Luminarie Dirt Depreciation
Figure 16.2 (from Figure find maintenance category and then use Figure 16.2 )

15. LLD
Data for fluorescent lamps

16. LDD
Ref: Tao and Janis (2001)

17. Example for LOF and LLF calculation
HID mercury lamps (250 W) in fixture type 18 (Figure 16.6), magnetic ballast, voltage oscillation 2%, cleaning period is
12 months, very dirt environment.
- Voltage oscillation (drop) of 2% →Table 16.4 → VF=0.95
- Magnetic ballast →Table 16.5 → BF=0.95 (additional table)
LOF=VF*BF=0.95*0.95=
From Figure 16.6 maintenance category is V. Very dirt environment and cleaning period 12 months→ Figure → LDD=0.7
Mercury lamps (250 W) → table → LLD= 80%.
LLF=LDD*LLD= 0.7*0.8=0.54

18. Rated lamp lumens per fixture F
F = Number of lamps per fixture × Lumens per lamp
Number of lamps per fixture – from Figure 16- 6
Lumens per lamp –manufacturer or table in your book

19. Example for calculation of F
HID mercury lamp (250 W) in fixture type 18 (Figure 16.6), magnetic ballast, voltage oscillation 2%, cleaning period is 12 months, very dirt environment.
Fixture type 18 → Figure 16.6 → Only one lamp per fixture
Mercury lamp (250 W) → Table 15.4 (initial lumen) → lum
F=1*12500=12500 lumens

20. Finally calculate the number of luminarie - N
N = E × A / (F × LLF × LOF × CU)

21. Handouts Step-by-step procedure Best source is IESNA Handbook
General guidance in your textbook
Best source is IESNA Handbook
IESNA - Illuminating Engineering Society of North America
Focuses much more on quality issues

22. Distribution of luminarie S/MH
Goal is to have even illumination

23. Table to calculate S for S/MH ration
Ref: Tao and Janis (2001)

24. Summary
Calculate CU
Calculate number of fixtures need for a specific space
Do not ignore S/MH ration when you distribute lamps

25. What is the difference between this two pictures

26. Daylighting computer simulation
Radiosity method

27. What about lighting quality?
Zonal cavity calculations focus on light quantity
Quality can not be ignored
CRI, evenness of illumination, transition between light and dark, flicker, glare, color temperature
Quality is very important

28. Daylighting Scientific and psychological studies have found:
People prefer buildings where changes in sunlight exterior affect interior lighting
Properly lit spaces are preferred to underlit or overlit spaces
Diffuse lighting is preferred to direct lighting
North sky lighting is ~universally preferred

29. What are problems with daylighting?
Can require extensive controls
Requires extra hardware to avoid direct lighting
Can require expensive glazing
Can damage works of art
Need to limit the amount of heat associated with solar gains

30. Strategies for Daylighting
Orient your building on an East-West axis
Limit direct sunlight with exterior shades, light shelves, clerestory windows, translucent glazing
Control glazing and conventional lighting with controls
Occupancy sensors
Automatic blinds
Light-level sensors

31. Reading Assignment Tao and Janis
Chapter 16 and section 17.1, 17.2, and 17.4