1) This classroom has _______.

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# 1) This classroom has _______. - PowerPoint PPT Presentation

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 _______.
• 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
S/MH
• Fixture height to have even illumination
• 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)
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
Summary
• Calculate number of fixtures need for a specific space
• Calculate CU
• Tuesday
• Accent lighting
• Daylighting
• Lighting quality
• Thursday
• Review