Durability - Retail lighting
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 performance issues for lighting options.
Introduction
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 100m² of floor area is to be 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 lamplumens 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 which 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
Gives 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 16mm (T5) are generally specified as they are the most
efficient type.
• Compact fluorescent lamps (CFL)
These are are a miniature version of the fluorescent tube and should be
rated above 11W. 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 life cycle costs
Lighting may account for as much as 50% of energy bills in a retail premises Lifetime time costs can be further 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
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 5
– 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 which allows 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 the lamps and
luminaires to maintain illuminance at acceptable levels. Dirt and dust
can reduce light output 20 – 30% after 2 years with no cleaning.
There is a wealth of lighting design guidance published by CIBSE,
the Society
of Light and Lighting and the 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.
Installation issues
Refer to BS 8000–16. Good preparation is essential:
• Surfaces should be clean and dry
• If required, apply the correct primer, filler, back–up or
bond break.
• Sealants should be given the correct profile: the exposed face
of triangular fillet joints should ideally be convex or flat, preferably
not concave. Rectangular joints should be finished flat or slightly concave.
Specification options
| Capital cost £/m |
Net present value for 60 years £/m | Average Service Period hours for lamp |
Energy consumption* | |
| Internal lighting | ||||
| Tubular fluorescent lamps 3 x T8, 18 watt. Luminaire: recessed in ceiling, 600 mm x 600 mm, with stove enamel steel or aluminium spine, UV stabilised diffuser | 97 | 526 | 13,000 | 12-18% |
| Compact fluorescent lamp, 28 watt. Luminaire: ceiling mounted, circular polycarbonate cover, aluminium body. | 45 | 329 | 9,000 | 18% |
| Tungsten filament bulb 60 watt. Luminaire: glass diffuser fitting. | 35 | 450 | 1,000 | 100% |
| External lighting | ||||
| High pressure sodium lamp, 70 watt floodlight. Luminaire die cast aluminium polyester powder coated, with control gear IP65 rated for external use | 175 | 836 | 24,000 | 11% |
| Metal halide lamp, 70 watt floodlight. Luminaire die cast aluminium polyester powder coated, with control gear IP65 rated for external use | 175 | 1,183 | 11,000 | 15% |
| Induction lamp, 70 watt floodlight. Luminaire die cast aluminium polyester powder coated, with control gear IP65 rated for external use | 317 | 1,223 | 60,000 | 18% |
* Energy consumption figures, based on DETR data, are relative to a tungsten filament bulb, which has been included in the analysis for comparative purposes only
Table notes
• The component and cost data for the different luminaires and
lamps is not directly comparable as 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 a 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 which satisfy project-specific
criteria.
• A discount rate of 3.5% is used to calculate net present values.
First published in Building 2005
Further information
Building LifePlans provides latent defects warranty
for all buildings.
BLP Construction Durability Database at www.componentlife.com
provides durability information for building components.
Further information contact peter.mayer@buildinglifeplans.com
or telephone: 020 7204 2441.
