Efficient lighting and daylighting

Lighting levels required depends on the property type

The illuminance is the total amount of light (flux) falling on a surface and is measured in lux (SI uni). Lamp output is measured in lumens. Lux = lumens per square metre. Determining lighting levels depends on the design of the building

  • Daylighting (Advantages: Energy savings, positive psychological impact, increased productivity. Disadvantages: Increase heat load, costly to integrate with artificial light, glare and internal shadows)
  • Daylighting + Artificial lighting
  • Artificial lighting alone

    Table of Lighting Levels (AS 1680)

    Table of Lighting Levels (AS 1680)

Ways to maximise daylight

  • Light shelves: High reflectance upper surface, reduces glare, improves light distribution, better in temperate climates. However, can reduce overall daylight in some conditions
  • Laser cut panels:  Acrylic panel mounted internally or externally with laminate, low glare, high level of light deflection, general increases in light distribution achieved. However, some distortion of outside view and relatively expensive
  • Reflective blinds/ louvres: Placed externally, internally or between panes, manual or automatic control, can increase daylight penetration into space in sunny conditions. However, it can obstruct view and cleaning maybe difficult

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Types of  artificial lamp are available

Types of Artificial Lamps

Types of Artificial Lamps

The most efficient are

  1. High-pressure sodium lamps 183-200 lm/W
  2. High intensity discharge lamp 150 lm/W
  3. Conventional Fluorescents
  4. Compact Fluorescents
  5. LED 131 lm/W

Lamp efficacy (LPW) = L (lumens)/ W (Watts)

where L = Light emitted; W = Power required

Lamps have varying efficacy

Lamps have varying efficacy


How do we calculate the energy consumption of a lighting system?

Energy (Wh) = Sum of Number of lamps (N)*Wattage of lamp (W)*Operating Hours (H)


Considerations for artificial lamps

  • cost
  • size
  • life time and reliability
  • colour properties
  • dimmability
  • simplicity and convenience in use
  • disposal
  • environmental effects
  • lumen maintenance


Strategies to reduce lighting energy use

Low cost techniques

  • remove lamps
  • replace lamps to more efficient ones
  • improve user behaviour
  • improve lamp maintenance

Retrofit or redesign

  • Introduce task oriented lighting
  • change colour of walls, floors and ceiling
  • Increase use of daylighting
  • Install automatic control system (motion sensors or time of day)

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