Define Needs: Design

The primary objective of any lighting scheme should be to maximise the effectiveness of the light.

The following design criteria should be considered:

• Luminous efficacy: How much light a lamp produces for a given input power, measured in lumens per watt. This should be maximised to achieve energy efficiency savings.
  
  
• Colour appearance:  What colour the ‘white’ light appears measured in Kelvin. The correct approach will depend on the nature of the lit environment, for example whether the lit environment should feel ‘warm’ or whether the lighting is designed to provide ‘impact’ perhaps for display purposes.
  
  
• Colour rendering: How faithfully colours are rendered by the light, measured by the colour rendering index (ra).
  
  
• Light distribution: How much light should fall on the walls, ceiling and floor. Most environments require a balance of horizontal and vertical lighting.
  
  
• Luminaire positioning: Where luminaires should be positioned in order to achieve optimum light distribution.
  
  
• Luminaire LOR: How much light the luminaire emits – often determined by shape and use of reflective material.
  
  
• Aesthetics of luminaires: Where the luminaires can be seen the shape and design should be considered.
  
  
• Quality and regulatory compliance: Providing adequate lighting is a legal obligation and health and safety issue.