1) This classroom has _______.

1. 1) This classroom has _______. • Too much lighting • Not enough lighting • About the right amount of lighting

2. 2) For which of the following conditions would you increase the weighting factor by +1 in a lighting design? • A room used exclusively by high school students • A circular room with mirrors for walls • A room used exclusively by government employees (i.e. speed/accuracy of task not important) • A room used for cutting dark stone

3. Objective • Use room geometry to calculate coefficient of utilization (CU)

4. Now what? • We now know how much light we need. • How do we get it? • Zonal cavity method • Calculate CU • How much light makes it from the fixture to the work surface of interest • Graphical methods (similar to stress strain) • Ray tracing • Computationally intensive

5. Illumination Calculation • Iws = N × LPL × LOF × CU / A • N = number of fixtures • LPL = rated lumens per fixture • LOF = lamp operating factor • Ballast, voltage, temperature, position (HID) • CU = coefficient of utilization • Fraction of light that meets the work surface • A = room area

6. Lamps are Not the only thing • Fixtures (luminaires) • Lamp type and number • Power requirements • Ballast • Application requirements • Mounting • Fixture control • Special features • Distribution

7. Ref: Tao and Janis (2001)

8. S/MH • Fixture height to have even illumination

9. 3) In lighting design, the coefficient of utilization __________. • Determines the fraction of light fixtures in a room that are actually used. • Measures the fraction of emitted light that reaches a working surface. • Is lower in a room with light-colored walls than in one with dark walls. • Depends on the type of task performed, accuracy required by the task, and on the ages of occupants in a room.

10. Zonal Cavity Method • Purpose is to get CU “fixture efficiency” • What parameters do you need?

11. Figure 16-1 Ref: Tao and Janis (2001)

12. 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

13. Reflectance • Experience • White ceiling, Rc = 70 – 80 % = ρc • White walls, Rw = 60 - 70 % = ρw • Medium to light colored walls, Rw = 50 % =ρw • Dark wood paneling, Rw = 25 % = ρw • Floor, Rf = 10-30 % = ρf • Convert to effective reflectances (ρcc, ρw, ρfc) • Tables in Tao and Janis (pg 92-93, 102-107) or from manufacturer

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

15. Calculations (continued) • Table 16.8 • ρcc and ρfc (assume ρfc = 20% if no other information given) • Table 16.9 • CU Multiplier if ρfc ≠ 20% • Fixture table • CU based on ρcc , Rw,RCR • Use CU by multiplier from step 4.

16. Example • Classroom (30 × 30 × 9) • White ceiling, blackboards on 2 sides, light floor • Students working on desks • Fluorescent fixtures at ceiling level • Use standard tables

17. Data So Far • PAR = 2 × (L+ W)/(L × W) = 120ft/900ft2 • CCR = 2.5 × PAR × hc = 0 • RCR = 2.5 × PAR × hr = 2.17 • FCR = 2.5 × PAR × hf = 0.83 • ρcc = Rc = 70% (b/c CCR = 0) • ρrc = Rw = 30% • ρfc = 20% (assumption)

18. Variations • Fixture 2 (pg 92), 1 ft from ceiling • Actual fixture, original height • Original fixture, 30% reflective floor

19. Fixture 2 • PAR = 2 × (L+ W)/(L × W) = 120ft/900ft2 • CCR = 2.5 × PAR × hc = 0.33 • RCR = 2.5 × PAR × hr = 1.83 • FCR = 2.5 × PAR × hf = 0.83 • ρcc = 64% (Table 16-8) • ρrc = Rw = 30% • ρfc = 20% (assumption, could use Table 16-8)

20. Ref: Tao and Janis (2001)

21. Actual Fixture • PAR = 2 × (L+ W)/(L × W) = 120ft/900ft2 • CCR = 2.5 × PAR × hc = 0 • RCR = 2.5 × PAR × hr = 2.17 • FCR = 2.5 × PAR × hf = 0.83 • ρcc = Rc = 70% (b/c CCR = 0) • ρrc = Rw = 30% • ρfc = 20% (assumption)

22. More Reflective Floor • PAR = 2 × (L+ W)/(L × W) = 120ft/900ft2 • CCR = 2.5 × PAR × hc = 0 • RCR = 2.5 × PAR × hr = 2.17 • FCR = 2.5 × PAR × hf = 0.83 • ρcc = Rc = 70% (b/c CCR = 0) • ρrc = Rw = 30% • ρfc = 30% (given, could use Table 16-8 Tao and Janis)

23. 4) If a building owner hires Persephone to determine the amount of lighting in an existing building, Persephone would need to know which parameters? • Type of activity performed, age of occupants, speed needed to perform activities in the building • Shape of the rooms, distance from light fixtures to work surfaces, reflectance of surfaces, types of light fixtures in the building • Color rendering index, evenness of lighting, thermal properties of lighting in the building

24. 5) If a developer hires Francisco to determine the required lighting levels for a new building, Francisco would need to know which parameters? • Type of activity performed, age of occupants, speed needed to perform activities in the building • Shape of the rooms, distance from light fixtures to work surfaces, reflectance of surfaces, types of light fixtures in the building • Color rendering index, evenness of lighting, thermal properties of lighting in the building

25. Illumination Calculation • Iws = N × LPL × LOF × CU / A • N = number of fixtures • LPL = rated lamp lumens per fixture • LOF = lamp operating factor • Ballast, voltage, temperature, position (HID) • CU = coefficient of utilization • Fraction of light that meets the work surface • N = Iws× A / (LPL × LOF × CU)

26. Distribution • Direct 90 – 100 % downward • Semi-direct 60-90% down, rest upward • Direct-indirect/general diffuse • Semi-indirect • Indirect

27. Ref: Tao and Janis (2001)

28. Ref: Tao and Janis (2001)

29. Summary • Calculate number of fixtures need for a specific space • Calculate CU • Tuesday • Accent lighting • Daylighting • Lighting quality • Thursday • Review