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Lighting Design Calculations - Lecture Slides | ARE 346N, Lab Reports of Architecture

The University of Texas at AustinArchitecture
Prof. Jeffrey A. Siegel

Material Type: Lab; Professor: Siegel; Class: BUILDING ENVIRONMENTAL SYSTEMS; Subject: Architectural Engineering; University: University of Texas - Austin; Term: Unknown 2001;

Typology: Lab Reports

Pre 2010

Uploaded on 08/30/2009

koofers-user-13s
koofers-user-13s 🇺🇸

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Lighting Design Calculations
• What is the space being used for?
• How much light do the occupants need?
• What factors will influence light levels?
• Preliminary calculations
• What fixtures/lamps/ballasts should you use?
• Where should you put them?
• Text 16.1-16.6, 17
Objective 1
• Determine required lighting levels
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Download Lighting Design Calculations - Lecture Slides | ARE 346N and more Lab Reports Architecture in PDF only on Docsity!

Lighting Design Calculations

  • What is the space being used for?
    • How much light do the occupants need?
  • What factors will influence light levels?
    • Preliminary calculations
  • What fixtures/lamps/ballasts should you use?
    • Where should you put them?
  • Text 16.1-16.6, 17

Objective 1

  • Determine required lighting levels

Do Not Ignore Quality Issues

(Table 16-1A)

  • Glare
  • Comfort
    • Similar to thermal comfort
  • Evenness
    • Around work area
    • On surfaces
  • Color issues
    • CRI, color temperature
  • Vertical vs. horizontal

Handouts

  • Step-by-step procedure
    • Detailed in Chapter 16 of your text
  • Best source is IESNA Handbook
    • Focuses much more on quality issues
    • Need to reference it for specific spaces

Examples

  • Drafting in 5th^ floor lab
  • Computer laboratory
    • In the same room?
  • Sushi counter in a restaurant
  • Dining area in same restaurant

Lighting Design Objective 2

  • Use room geometry to calculate coefficient of utilization (CU) - Fixture efficiency - Fraction of light that makes it from the fixture to the work surface
  • Any questions from Dr. Novoselac’s lecture?

Illumination Calculations

• E = LLF × CU × F / A

  • F = number of fixtures × light output per fixture
  • LLF = light loss factor (VF × TF × BF × LSDF)
  • CU = coefficient of utilization
    • Fraction of light that meets the work surface
  • A = room area Ref: Tao and Janis (2001)

Reflectance

  • What is the difference between base and effective reflectances?
  • How does Table 16.6 affect your calculation of reflectance? - Why does Rw =^ ρw?
  • How does Table 16.7 affect your calculation of 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)
    • Table 16.6 or from manufacturer

Calculation Procedure

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

Calculations (continued)

  1. Table 16.
    • ρcc and^ ρfc (assume^ ρfc = 20% if no other information given)
  2. Table 16.
    • CU Multiplier if^ ρfc ≠^ 20%
  3. Fixture table
    • CU based on^ ρcc , Rw,^ RCR
  4. Use CU with multiplier from Step 4.

S/MH

  • Fixture height to have even illumination

Data

  • PAR = 2 × (L+ W)/(L × W) = 120ft/900ft^2
  • CCR = 2.5^ ×^ PAR^ ×^ hc = 0
  • RCR = 2.5^ ×^ PAR^ ×^ hr = 2.
  • FCR = 2.5^ ×^ PAR^ ×^ hf = 0.
  • ρcc = Rc = 70% (b/c CCR = 0)
  • ρw = 30%
  • ρfc = 20% (assumption)

Variations

  • Fixture suspended 1 ft from ceiling
  • 30% base reflective floor
  • Default fixture (from Text)

Illumination Calculation

  • E = Iws = F/A^ ×^ LLF^ ×^ CU
  • F = num. of fixtures × rated lamp lumens per fixture
  • LLF = light loss factor
    • Ballast, voltage, temperature, position (HID)
  • CU = coefficient of utilization
    • Fraction of light that meets the work surface
  • A = room area

Light Loss Factor (LLF)

• LLF = VF × BF × TF × LSDF

S/MH

  • Fixture height to have even illumination

Summary

  • Calculate number of fixtures need for a specific space - Calculate CU
  • Do not ignore S/MH

Example

  • 100 ft^2 diameter circular room
  • 30 ft high
  • Requires 50 fc on work surface
  • Light-midtone walls (R=40%)
  • Light gray ceiling (R=50%)
  • Dark and shadowed floor (R=20%)
  • Work surface is 3 ft from floor
  • Fixture is 2 ft from ceiling, 2000 lumen lamps
  • Fixture S/MH = 1.

Summary

  • Calculate number of fixtures need for a specific space - Calculate CU
  • Do not ignore S/MH

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 more important
  • Daylighting is one strategy to reduce lighting energy use and increase lighting quality - Use the sun for illumination

Commercial Building Costs

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

Other Lighting Material

  • Lighting spread
  • Accent lighting
  • More sophisticated lighting design
  • Lighting controls
  • Daylighting calculations