To achieve effective energy savings, the next revision of Part L of the Building Regulations must drop its crude metrics for a sophisticated approach to low energy that includes controls, operational load and daylight linking, says Iain Carlile

‘Right light, right place, right time’ is a philosophy that my practice, dpa lighting design, has been applying to its projects for a number of years.

Giving due consideration to selecting the right light source and luminaire combination suitable for the task and, through the use of an appropriate control system, the hours and the dimming levels at which it operates.

This approach ensures a visual quality and an efficient use of energy in the installed scheme.

New or revised legislation can affect our work and the way we apply this philosophy. Some legislation, although well meaning in what it aims to achieve, neglects the best approach to accomplish its requirements.

The most obvious and recent example of this was the introduction of the latest edition of Part L of the Building Regulations in October 2010.

Ludicrous situation

Part L is correct in its requirement to reduce energy consumption, but the metrics used for lighting are quite crude and predominantly only cover the efficacy of the luminaire — not the total energy consumption of the lighting system.

This leaves us in a ludicrous situation. The lighting scheme can comply with the requirements of Part L but still waste energy through the unnecessary lighting of unoccupied or daylit areas.

For example, look at many commercial properties where all of the lighting is on throughout the night when the space is unoccupied. These installations can have efficient luminaires and lamps, achieving low installed electrical load per unit area and high luminaire efficacies. But the absence of simple occupancy controls means the lighting can remain on for more than twice the required operational hours, wasting a huge amount of energy.

Vast energy wasting in commercial properties

The installation may meet the requirements of Part L, yet in fact the installation can be quite wasteful of energy because the lighting is not switched off when it is not required.

Recent advances in technology make it possible to specify LEDs for ambient lighting that emit an excellent quality of light across the visual spectrum, with a colour temperature and colour rendering properties that compare favourably with tungsten lamps.

Efficacy requirements

However, many of these LEDs do not meet the efficacy requirements of Part L on their own and it would therefore not be possible to design a lighting scheme predominantly using these light sources. But because Part L’s main consideration is the efficacy of the luminaire, it is possible to design a scheme utilising compact fluorescent lamps, without even simple lighting controls, that would consume more energy than an equivalent LED scheme utilising a lighting control system to both dim and switch off the lighting as appropriate.

The compact  uorescent scheme would have a lower visual quality and greater energy consumption than the LED scheme, directly contradicting the spirit of the legislation.

We consider a lighting control system to be an essential part of any lighting scheme to allow for scene setting, switching off of unnecessary lighting in unoccupied spaces and daylight linking where appropriate.

In hospitality applications the actual running load is typically 40 per cent less than the total installed electrical load for the lighting. Many lighting control systems can be retrofitted to an existing lighting installation that, after a payback period, can present savings to the client through the ongoing reduction in energy use.

A number of lighting control systems also offer the ability to log data and feedback information, helping staff to manage and maintain the installation.

Considering the many benefits that lighting control systems present in both new build projects and refurbishment of existing building stock, it is frustrating that very little credit or true recognition of their energy saving benefits are identified in Part L.

Resolving the situation

For this situation to be resolved, future revisions of Part L must change the metric used for measuring the energy efficiency of a lighting installation.

We must as an industry challenge the existing legislation and push for a suitable metric that considers not just the efficacies of lamps and luminaires but also includes factors such as lighting controls, dimming levels, hours of operation, daylight linking and presence detection.

Only then will we have legislation that allows the intelligent application of the ‘right light, right place, right time’ philosophy.

Personally, I am glad to see that the Society of Light and Lighting is pushing for a move to systems-based targets in the next revision of Part L.

Iain Carlile is a senior designer at dpa lighting design

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