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

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1) This classroom has _______.

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### 1) This classroom has _______.

• Too much lighting

• Not enough lighting

• About the right amount of lighting

### 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

### Objective

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

### 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

### 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

### Lamps are Not the only thing

• Fixtures (luminaires)

• Lamp type and number

• Power requirements

• Ballast

• Application requirements

• Mounting

• Fixture control

• Special features

• Distribution

Ref: Tao and Janis (2001)

### S/MH

• Fixture height to have even illumination

### 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.

### Zonal Cavity Method

• Purpose is to get CU “fixture efficiency”

• What parameters do you need?

### Figure 16-1

Ref: Tao and Janis (2001)

### 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

### 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

### 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

### 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.

### 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

### 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)

### Variations

• Fixture 2 (pg 92), 1 ft from ceiling

• Actual fixture, original height

• Original fixture, 30% reflective floor

### 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)

Ref: Tao and Janis (2001)

### 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)

### 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)

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

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

### 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)

### Distribution

• Direct 90 – 100 % downward

• Semi-direct 60-90% down, rest upward

• Direct-indirect/general diffuse

• Semi-indirect

• Indirect

Ref: Tao and Janis (2001)

Ref: Tao and Janis (2001)

### Summary

• Calculate number of fixtures need for a specific space

• Calculate CU

• Tuesday

• Accent lighting

• Daylighting

• Lighting quality

• Thursday

• Review