OPINION
Stairwell to heaven

…well, maybe not, but there’s money to be saved by looking at alternatives to the mainstay of stairwell lighting – the 2D bulkhead fitting, as Dave Tilley discovers

Stairwells do not conjure up a great deal of enthusiasm or excitement from lighting industry professionals. Then again, why should they? The stairwell is generally a quiet space, often in bare concrete with little scope for creative design.

Even lighting designers often leave the selection of fittings to the electrical contractor. But times are changing.

With rising energy prices and legislation that mandates energy efficiency, even the humble stairwell is now under the spotlight.

If, for example, you are working on an eight-storey office block with a stairwell at either end there may be a clue to this sudden fascination in stairwell lighting. Based on standard practice over the past few years, there could be as many as 86 bulkhead fittings in the stairwells.

There are a number of reasons for this.

  • The installer was not sure of the required light levels and applied the rule of ‘better safe than sorry’.
  • The ‘better safe than sorry’ rule was also applied to the emergency lighting.
  • The 2D bulkheads looked better arranged in a particular pattern.
  • A stairwell, unusually bereft of 2D bulkhead fittings


    Do the math

    A few calculations will explain why stairwell lighting has become an area to focus on.

    Eighty-three 2D bulkheads operating for 8,760 hours consume 25,500kWh and are responsible for the emission of 14.13 tonnes of carbon dioxide.

    At £0.10 per kilowatt-hour, they cost £2,550.00 a year to run, and a further £170.00 in Carbon Reduction Commitment tax.

    So it costs £2720.00 to illuminate a space that is rarely used and for much of the time is flooded with daylight. I think the reason for the sudden interest in stairwell lighting is clear. In fact finance directors and energy managers can be forgiven for spending some time reviewing this often overlooked area.

    Before we start, however, we must be mindful in the search for efficient lighting that stairwells are generally designated fire escape routes.

    Perhaps, like me, you have searched for the elusive LED bulkhead. I say elusive because there are a vast number of fittings that are promoted as alternatives to 2D but the lumen output of the ones I have examined is too low for the fitting to be classified as a replacement – please note electrical distributors – or the price of those that do have a comparable lumen output is just too high to make financial sense.

    On this point it is refreshing to see that Fern Howard is approaching LED bulkhead design with thought and structure. The company is developing a range of LED bulkheads that will give designers and specifiers qualified options.

    The table below demonstrates the scope of savings possible.

    The combination of a GE Lighting 2D Watt-Miser and a bulkhead with intelligent controls demonstrates the potential to save significant amounts of energy without compromising light output.

    The savings achieved by introducing intelligent bulkheads are possible through either daylight linking, occupancy or a combination of both.

    It is worth noting that if daylight linking is used exclusively, without manual switching, the bulkheads will operate all night.

    Like most things in lighting design and specification, understanding usage and movement patterns is essential to the specification.

    Outlined below is a five-year return on investment model for the 2D Watt-Miser and intelligent controls.

    A three-year ROI that does not include installation may not impress every financial director. However, to do nothing will mean increasing energy and maintenance costs which in the current climate will only get worse.

    Words of caution

    Before everyone rushes off to specify and install intelligent bulkheads, a few words of caution.

  • If the stairwell is used as a major staff circulation route the savings will be lower. The control settings will have to be refined to prevent frequent switching and protect the lamps.
  • The intelligent bulkhead must be in a position that guarantees full illumination when people access the stairwell and move between floors. All movement patterns must be accounted for. This is particularly important if you are considering point-for-point replacement.
  • The emergency lighting system and structure must not be compromised.

    THE LIGHTING ECONOMIST’S VERDICT

    There is significant potential to save energy use for lighting in stairwells and similar areas.

    The usual problems of choosing LED or intelligent fluorescent luminaires are overshadowed by the more important issue of safety, both for escape and general movement.

    I conclude that in the current climate, as energy prices and legislation force their hands, designers and specifiers will specify LED luminaires rather than more traditional intelligent products.

    davidt@lo2ltd.com

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