Efficient by design, wasteful in the real world

Lighting designers are frustrated when their carefully considered low-energy schemes are operated by people who neither know nor care how it should work, says Kevan Shaw

Lighting has been subject to the Building Regulations for a fair number of years. The aim has been to try to drive down the total energy needed to operate a building.

The measures used have been somewhat crude sofar. We started off with limitations on lamp efficiency. These proved somewhat unreliable and in certain cases increased the power used because higher efficiency usually went hand in hand with higher output.

We then moved on to the current situation in which we must meet a certain circuit wattage ef ciency. At least this encompasses the use of relatively efficient fittings and gear, but the thresholds set are not easily improved upon without severely restricting the kind of lighting that may be used in the future. Neither of these approaches, nor the alternate requirements to limit the total circuit watts per square metre for lighting load, addresses the real question of how much energy is actually used to provide light.

As has been made clear month after month in this magazine’s Named and Shamed column, the biggest waste of energy is not what is used to create light but when it is used. The time factor is the key.

Five years ago a measure that includes the time factor was enshrined in EN 15193, Energy Performance of Buildings – Energy Requirements for Lighting. This is the lighting energy numeric indicator (LENI).

Incredibly dificult and complex

As with many standards, the presentation of this makes it look incredibly dif cult and complex to calculate but, in reality, it is not at all difficult and all the necessary numbers should be to hand for a properly designed project. This is expected to be the measure used in the forthcoming 2013 revision to the Building Regulations and is supported by pretty much all of us involved in lighting, from manufacturers to designers. LENI does take proper account of several factors that have been neglected by previous approaches.

These include daylight availability as well as occupancy of spaces. It also includes provision for pre-set lighting controls so, at last, the lighting designer has considerable freedom in creating complex lighting schemes that may include several different sets of lights in the same space that are used at different times.

Obviously, employing a professional lighting designer to create good lighting and manage the conformance to the appropriate LENI becomes much more attractive and we lighting designers have to step up and take responsibility for this.

So what comes next? Well the Building Regulations only de ne what can be built and have nothing to say about how a building is operated after completion. To really give LENI some teeth there will need to be some further legislation that requires buildings to be operated within the energy use targets de ned in the design stage.

All the issues we see with lights left on wastefully could be addressed if achieving the LENI became mandatory when the building is handed over. This is not so far fetched. It is mandatory to have separate load metering and the European standard does describe how LENI is to be derived from metered measurements.

As a lighting designer it would make me happy for the lighting to be operated the way I designed it to be used rather than at the whim of facilities managers who neither know nor care how we expected the project to look.

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Kevan Shaw is design director at KSLD

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