Power Efficiency Guide

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Up to the twenty-first century little effort had been made to limit the amount of energy used for the lighting of buildings by legislation; but a start was made by Part L of the Building Regulations of 1995, dealing with the conservation of fuel and power; this was a start to limiting the amount of energy used for lighting in buildings, and this coupled with the increased efficacy of the lamps and light fittings available from the lighting industry, had a material effect upon the energy demand.

In 2002, revisions to Part L made it a requirement to consider the need for 'energy efficient lighting' more seriously, and architects should be aware of the current regulations, which in themselves will no doubt be further updated and modified, to increase the need for further energy savings for the future.

The new Part L requires that 'Reasonable provision shall be made for the conservation of fuel and power in buildings other than dwellings, by . . . installing in buildings artificial lighting systems which are designed and constructed to use no more fuel and power than is reasonable in the circumstances and making reasonable provision for controlling such systems'. There is some flexibility for lighting designers to comply with the regulations, and there is every reason for the spirit of the regulations to be wholeheartedly adopted.

The regulations are divided into two parts, the first (Part L1) dealing with dwellings, and the second (Part L2) with non-domestic buildings.

The latter takes in offices, industrial buildings and those of multi-residential use, such as hotels, hostels, old people's homes, hospitals and boarding schools. This is a very broad sweep of the majority of buildings, and architects should be aware of the implications ... it will not be sufficient to say that your client has demanded illumination levels of 1000 lux in a hotel foyer when to provide this level the amount of energy used is far in excess of the amount allowed for this type of space.

To give an example of the legislation the following is a quotation from Part L2: This refers to general lighting efficiency in office, industrial and storage buildings:

1.43 Electric lighting systems serving these buildings should be provided with 'reasonably efficient lamp/luminaire combinations.' A way of meeting the requirements would be to provide lighting with an initial efficacy averaged over the whole building of not less than 40 luminaire-lumens/circuit watt. This allows considerable design flexibility to vary the light output ratio of the luminaire, the luminous efficacy of the lamp, or the efficiency of the control gear.

A table of lamps which meet the criteria for general lighting follows:

Light source

Types and rating

High pressure sodium Metal halide Induction lighting Tubu lar fluorescent

Compact fluorescent (CFC) Other

All types and ratings

All types and ratings

All types and ratings

26 mm. diam. (T8) lamps 16 mm. diam. (T5) lamps rated above 1 1 watts, provided with high efficiency control gear. 38 mm. diam. (TI2) linear fluorescent lamps 2400 mm. in length.

All ratings above II watts

Any type and rating with an efficiency greater than 50 lumens/ circuit watt.

Whilst this clearly precludes the use of tungsten lamps for general use, they can still be used in some areas which may demand their use; where the average over the whole building does not exceed the predetermined 40 luminaire-lumens/circuit watts . . . there is flexibility.

A major difference in the new regulations is that they apply to display lighting, defined as 'lighting designed to highlight displays of exhibits or merchandise.' (Examples of display lighting are included in the Case Studies shown later, a good example being the Sainsbury Store in Greenwich (Case Study pp. 164-167) where high levels of environmental lighting are available during the day by the use of natural light from roof lights, but where in terms of Part L the overall energy use is below the limits of the requirements.)

Part L of the building regulations encourages the use of daylight linking, stressing the relationship between the available daylight, and controlled artificial light sources. Daylighting can be at the heart of energy savings in buildings, and whilst in the early twentieth century this was largely forgotten, at the beginning of the twenty-first it has been shown to be a key to the future.

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