Good lighting design can give retailers a competitive advantage as well as being energy efficient. Peter Mayer of Building LifePlans looks at the whole-life costs of common lighting options

Lighting systems in new buildings or in replacement work are required by approved document Part L2 of the Building Regulations to be energy efficient where more than 100 m2 of floor area is serviced by artificial lighting. Part L2 sets an efficiency level of 50 lamp lumens per circuit watt for general lighting – this measure includes the efficiency of the lamp and its associated control gear, such as the Ballast. For display lighting, the efficiency should be greater than 15 lamp lumens per circuit watt. An alternative approach is to ensure that more than

95% of the lighting comprises lamps of equal or better performance than the types that are considered in more detail below. Similar requirements and standards apply to Scotland.

Retail lighting options

Generally, energy-efficient lamps give low operational costs at the price of high installation costs. The exception is fluorescent lamps, which offer relatively low installation and operational costs. Other options include:

  • High-pressure sodium (SON) lamps: Give a yellowish light and are usually used externally.
  • Metal halide lamps: Give excellent white light with better colour rendition than sodium-based lamps. They are used for general and display lighting.
  • Induction lamps: Power for these lamps is passed without the need for physical conductors or electrodes. This results in long lamp service periods. Typically they are available as low-pressure mercury lamps.
  • Tubular fluorescent: These should be of the high-efficiency type coupled with a high-efficiency control gear that saves energy, eliminates flicker and extends lamp service period. Tubes of 16 mm (T5) are generally specified as they are the most efficient type.
  • Compact fluorescent lamps (CFL): These are a miniature version of the fluorescent tube and should be rated above 11 W. They provide maximum energy efficiency when switched on for more than four hours. These need specialist dimming equipment.
Alternative energy-efficient lighting solutions not specifically mentioned in the approved document include LED lamps and fibre optics.

Strategies to minimise lifecycle costs

Lighting may account for as much as 50% of energy bills in retail premises. Lifetime costs can be minimised by specifying the following:

  • Well-designed light fittings with high light output ratio (LOR). These typically incorporate diffusers and highly reflective reflectors to improve efficiency.
  • Retail design that incorporates as much natural daylight as possible. Refer to the CIBSE Daylighting and window design lighting guide. Research suggests natural daylighting can increase sales.
  • Automatic lighting controls. Photoelectric controls can be calibrated to balance artificial and natural daylighting so that electric lamps are dimmed or switched off when there is sufficient natural light.
  • Modular or prefabricated wiring systems. Retail interiors have a high churn rate, in that interiors may change every five to 15 years. Modular wiring systems can offer flexibility without the need to rewire. Design and installation cost savings of up to 30% are reported. Similar cost savings may be achieved on a churn refurbishment.
  • Lamps and lighting circuits with a higher energy efficiency. The approved document is merely a minimum standard. The CIBSE code for interior lighting defines good practice as a minimum 65 lamp lumens per circuit watt.
  • Internal surfaces and spaces that enhance lighting, such as high–reflectance surfaces.
  • Designs that allow simple and safe maintenance access.
  • Lamps and luminaires that are cost effective for the functional requirements of individual spaces.
  • Building log books, which are a requirement of the approved document. These include a cleaning regime for lamps and luminaires to maintain illuminance at acceptable levels. Dirt and dust can reduce light output 20–30% after two years with no cleaning.
There is a wealth of lighting design guidance published by CIBSE, the Society of Light and Lighting and BRE. The Carbon Trust provides advice related to energy efficiency measures.

Tax relief may be available to UK businesses through the Enhanced Capital Allowance scheme that encourages use of energy-efficient equipment.

Table notes

  • The component and cost data for the different luminaires and lamps is not directly comparable as the installations are for specific applications. The data gives an indication of the whole-life costs associated with typical installations as described.

  • Service periods are an average. Cost data is based on a usage of 10 hours a day, six days a week.

  • Electricity at 7.5p/kWh. Luminaires to relevant part of BS EN 60598. Costs include fixing and connection of luminaire but not wiring. An allowance for cleaning is included. No allowance for access. Luminaire replacement every 15 years.

  • The lamp and cost data is generic. Best value should be determined from a whole-life assessment of lighting options that satisfy project-specific criteria.

  • A discount rate of 3.5% is used to calculate net present values.

    Further information

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