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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

1) This classroom has _______.

  • Too much lighting

  • Not enough lighting

  • About the right amount of lighting


1 this classroom has

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

Objective

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


Now what

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

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

Lamps are Not the only thing

  • Fixtures (luminaires)

  • Lamp type and number

  • Power requirements

  • Ballast

  • Application requirements

  • Mounting

  • Fixture control

  • Special features

  • Distribution


1 this classroom has

Ref: Tao and Janis (2001)


1 this classroom has

S/MH

  • Fixture height to have even illumination


3 in lighting design the coefficient of utilization

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

Zonal Cavity Method

  • Purpose is to get CU “fixture efficiency”

  • What parameters do you need?


Figure 16 1

Figure 16-1

Ref: Tao and Janis (2001)


Calculate cavity ratios

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

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

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

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

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

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

Variations

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

  • Actual fixture, original height

  • Original fixture, 30% reflective floor


Fixture 2

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)


1 this classroom has

Ref: Tao and Janis (2001)


Actual fixture

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

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)


1 this classroom has

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


1 this classroom has

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 calculation1

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

Distribution

  • Direct 90 – 100 % downward

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

  • Direct-indirect/general diffuse

  • Semi-indirect

  • Indirect


1 this classroom has

Ref: Tao and Janis (2001)


1 this classroom has

Ref: Tao and Janis (2001)


Summary

Summary

  • Calculate number of fixtures need for a specific space

    • Calculate CU

  • Tuesday

    • Accent lighting

    • Daylighting

    • Lighting quality

  • Thursday

    • Review


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