Light work

The last few years have seen some significant changes in regulations pertaining to energy efficiency and best practice guidelines relating to ensuring a healthy and comfortably-lit environment. All of these changes have a bearing on the light sources that are selected for an office environment. The right lamps also play a role in minimising overheads, an important consideration for any commercial organisation.

The introduction of the Climate Change Levy in 2001, which added 0.43 p/kWh to electricity bills, has made people look more closely at their energy consumption. Similarly, Approved Document L2 of the Building Regulations, introduced in 2002, increased the pressure for energy efficient lighting. Towards the end of 2002 the Society of Light and Lighting took measures to clarify what is meant by best practice in lighting. This, among other things, placed more emphasis on lighting for people and less on lighting for vdus.

All of this focuses attention on the lamps and luminaires designed to give the best performance. Most advances in lighting are led by the improvement of existing lamps or design of new lamps, and the industry is working to develop lamps that will help building operators arrive at the best solution.

A case in point is the development of the TL5 fluorescent lighting system, which has become an industry standard. TL5 luminaires use fluorescent lamps that are only 16 mm in diameter instead of the 26 mm T8 lamps that used to be the first choice for office lighting. TL5 lamps with high frequency control gear offer higher energy efficiency, more light output and longer life.

Development of the product has continued and the latest Master TL5 lamps offer even higher efficiencies and can be retrofitted to any T5 luminaire. In addition, they use less mercury and materials and are fully recyclable, so they offer significant environmental benefits.

Such refinements are not confined to relatively new lamp types. There are many organisations using T8 lamps in their offices that would like to improve the lighting without going to the expense and disruption of installing a new system. The answer is to replace the T8 lamps with a more modern design of lamp that can be retrofitted to the existing fittings.

To some extent we saw this happen when triphosphor-coated lamps were introduced to replace the old halophosphor lamps that suffered from low efficiency and a light output that fell off rapidly as they got older (lumen depreciation). Recently developed T8 lamps offer a similar level of improvement over conventional triphosphor lamps. These give a higher light output with less lumen depreciation, as well as a more natural light and better colour rendering; they also last twice as long.

Longer life is an increasingly important consideration, as building operators come to consider the total cost of ownership of a lighting installation, rather than just the initial capital outlay and energy costs. The running costs include maintenance and, as health and safety regulations become tighter, changing a lamp is rarely as simple as sending an operative off with a ladder. Risks have to be assessed, precautions taken and there is often a considerable amount of paperwork to accompany any maintenance operation.

With longer life lamps, the relamping cycle is extended so they are changed less frequently, bringing immediate cost savings on labour, replacement lamps and minimised disruption to the office. When compulsory recycling for fluorescent and other discharge lamps comes into force in 2005, under the Waste Electrical and Electronic Equipment (WEEE) Directive, there will be further benefits to using long life lamps.

Most organisations will opt to employ specialist subcontractors to undertake their recycling and incur a cost per lamp, so fewer failed lamps will mean lower costs. Also, many firms now use group replacement strategies to have all of the lamps replaced at the same time, usually out of hours. This is very cost-effective but relies on predictable lamp life, so it makes sense to use high quality products whose life can be projected accurately.

Although incandescent lamps are not included in the WEEE Directive, the other arguments for choosing a long life still apply. The Building Regulations seek to limit the number of incandescent lamps that are used in buildings, but they are a very effective light source for accent and display lighting and low voltage dichroic lamps are widely used.

Again, ongoing investment in research and development has led to major improvements to previously standard designs. In the case of dichroic lamps, advances in design have led to longer life and higher light output, leading to greater performance and energy efficiency. In most dichroic lamps only about 10% of the electrical energy that goes into the lamp is converted to light – the rest is lost as heat.

Another example of an old leopard with new spots is the 2D fluorescent lamp, commonly used in ancillary areas such as stairwells, loading bays and plant rooms. This has been around for many years with very little change, but a new version, the PL-Q Pro, was launched recently. This offers a high light output per watt of power consumed, plus a life of 12 000 hours. These improvements have been achieved by paying close attention to every aspect of the design, from the materials that have been used to the accuracy of the glass bending.

Of course, good lighting isn't just about reducing the cost of ownership; it is vital to ensure a comfortably lit environment for staff. A number of studies have shown a direct link between comfort and productivity, and lighting plays a significant role in achieving comfort.

To that end, good lighting design seeks to ensure that the right lighting is provided in the right places in the office. Fluorescent lighting in the ceiling remains the mainstay for most offices but is now generally supplemented with other sources to increase lighting levels on the walls and ceiling rather than directing all of the light to the working plane.

Offices now tend to use a selection of different light sources, combining ceiling-mounted downlighting with wall-mounted uplighters, wallwashers and other forms of accent lighting. This provides a brighter, more spacious feel to the workplace, while ensuring that individual members of staff have sufficient light to carry out their tasks.

With the need to achieve a lower installed electrical load for the lighting, as dictated by the Building Regulations, many designers are choosing to supplement the fluorescent ambient lighting with high-efficiency light sources such as metal halide.

Metal halide is another source that has been in use for many years, but early versions tended to change colour as they aged and the colour varied between lamps, so they weren't ideal for office lighting. Newer versions use ceramic discharge metal halide technology, with improved colour stability, better colour rendering, higher efficiency and, again, longer life.

The examples given illustrate the importance of lamps to the performance of the whole lighting system and the continuous improvements that are being made, even to types that have been used for years. When it comes to choosing the most cost-effective lamps, there's more to it than simply picking the type that will fit in the luminaire; you must also consider the added value that comes from advanced design and engineering.