A new shop is about to open. The great and the good are assembled, the store is sparkling and the talk is all about energy efficiency and all the associated benefits.
Then the manager pushes open the door to the back-of-house area…
Don’t get me wrong, there are examples of good practice. For instance, John Lewis specifies back-of-house lighting in the same way it specifies lighting for the sales area. Sadly, it is the exception to the rule.
Back of house is often left to the electrical contractor who, in many cases, seems to see it as an opportunity to use all those spare luminaires.
Now, before contractors start firing off angry emails, it is possible that the installation has been designed – but the designs tend to be over-illuminated. In many cases, switch-start luminaires are installed. And a high proportion of lighting installations in back-of-house areas are never improved.
Back-of-house does not consume as much energy as the sales area, so there’s no reason not to include it in the lighting design, particularly when simple retrofit solutions can save energy and pay for themselves in less than two years.
To demonstrate the benefit of incorporating back-of-house in the store lighting design, I have provided a few examples of back-of-house lighting efficiencies. The numbers are from actual projects.
A great example of extreme lux levels is a staff kitchen illuminated by a twin 70W switch-start batten with prismatic diffuser. Interestingly, the majority of the back-of-house space was illuminated with the same luminaire.
The old twin 70W switch-start batten consumed 670kWh a year and was responsible for 0.4 tonnes of CO2 emissions. The new 28W 2D bulkhead uses just 110kWh a year, and is responsible for only 0.05 tonnes of CO2 emissions. So savings of 560kWh (worth £56) and 0.35 tonnes of CO2 can be made in a year.
The savings do not take into account the fact that, if a GE wattmiser 2D lamp is used, the operating wattage is reduced to 23W. Also a sensor could be incorporated, which would further improve efficiency.
The difference in lumen output between the two luminaries is significant, but the staff kitchen is small and the work area even smaller. This is probably an extreme example of an over-illuminated area, but it does demonstrate what happens if retailers leave back-of-house to chance.
Many happy returns
It is difficult to suggest a period to achieve return on investment, but in general for this type of initiative it would be about two years.
An example of using LED back of house can be demonstrated in a small stockroom with four aisles and shelving on either side. The stockroom was lit with 30 58W switch-start battens. Replace each of these with a 24W LED tube and you can cut energy use from 8,350kWh a year to just 2,800kWh, and carbon emissions from 4.6 tonnes to 1.6 tonnes. You’ve saved £547-worth of energy and three tonnes of CO2.
LED tubes are not high on my list of specified lighting products, but as I’ve said on many occasions, the specification of lamps and luminaires is about the application. In this case the LED tube delivers the right distribution of light and is particularly cost effective, the ROI is less than two years including installation.
I have detailed an example of a back-of-house area with a number of different spaces.
The example represents a small area. Depending on the type of sensor specified – built into the luminaire or located in the ceiling – the ROI can be estimated as about two years.
As well as the annual energy saving, there would be an annual reduction in carbon emissions of 1.05 tonnes.
If a typical back-of-house area is designed to incorporate appropriate lux levels, lamp and luminaire technology and lighting controls, annual energy savings of 60-70 per cent can be achieved.
The efficiency can be increased if the savings achieved through reduced maintenance and consumables is included.
You may have noticed that I have included reductions in carbon dioxide emissions in the calculations. Although the CRC legislation to encourage carbon reductions has had its teeth removed, there still remains an obligation on many UK businesses to reduce carbon consumption. It is also worth noting that, for many businesses, carbon emissions have a direct cost.
THE LIGHTING ECONOMIST’S VERDICT
Retailers and indeed all businesses with back-of-house areas must design and specify back-of-house in the same way they manage main areas.
Energy and maintenance efficiency should be part of business culture, not selective.
The management of back-of-house lighting specification and design can generate significant savings and importantly sends a positive message to staff: that the area they occupy is as important as that visited by customers.
- This special Lux conference for Facilities Managers is taking place on Thursday 19 May 2016 at the Cavendish Conference Centre in London. Entry is free to specifiers including facility managers, consulting engineers, estate managers, energy managers and others responsible for the management of lighting installations and their specification.
- View the full programme and register for your free place by clicking on the logo