The route to more efficient lighting

Published:  19 February, 2006

Lights
These modern high-bay and T5 fluorescent lighting fittings achieve over 70 luminaire lumens/circuit Watt — well above the 45 luminaire lumens/circuit Watt required by the forthcoming Building Regulations for commercial and industrial buildings.

The Government’s long awaited changes to Part L of the Building Regulations will set more onerous limits on the energy efficiency of lighting in domestic and non-domestic buildings. Just what’s involved is explained by HUGH KING.

Part L is the section of the Building Regulations dealing with conservation of heat and power from new and existing buildings, both domestic and commercial. It is being updated because the UK Government has a legal commitment to implement the European Directive on Energy Performance in Buildings (EPBD), which requires all new and existing buildings to be given an energy rating, and for new buildings to meet a minimum standard of energy efficiency.

The revisions to Part L, to be implemented in April 2006, will set maximum carbon-dioxide emissions for whole buildings. The changes have been designed to allow designers to choose practical and cost-effective solutions that best meet their needs. However, these revisions, the biggest yet, will have a significant effect on the building-services industry.

The sections on lighting have been revised, so let us attempt to explain succinctly just what will be required

First, Part L splits into two Approved Documents. L1A and L1B cover new and existing dwellings, and L2A and L2B apply to new and existing non-domestic buildings.

Dwellings — L1A & B

Beginning with dwellings, there are few surprises, and the targets can easily be achieved using modern equipment. The efficacy target of greater than 40 lumens/circuit Watt remains. However, guidance is given on determining the number of lighting points by floor area, rather than by the number of rooms. One energy-efficient fitting per 25 m2 and one per four fixed light fittings is now required. For external lighting, maximum Wattage is 150 W with automatic switching off — with photocell, PIR and time switch — or light fittings with sockets for lamps with over 40 lm/W (i.e. no GLS or halogen).

Non-dwelling buildings — L2A

For new buildings other than dwellings (offices, industrial and storage areas), the revised Part L requires an improved average efficiency for the whole building of not less than 45 luminaire lumens/circuit Watt (up from 40).

This is actually a big change, because previously most lighters took a short cut; by employing fittings from a given list of high-efficacy lamps they knew they would not fall foul of the requirements. Now they have to compute the figures. Furthermore there is no waiver for the first 500 W of installed lighting load. Many manufacturers will also have to upgrade their general luminaires to give higher LORs (light-output ratios), which could cause concerns with some office applications if user comfort is disadvantaged in the drive to save energy. That said, flexibility exists to trade off less efficient fittings against more efficient types within the building.

For lighting serving buildings other than offices, industrial and storage premises the average initial (100 h) lamp-circuit efficacy remains at not less than 50 lumens/circuit Watt.

Lighting controls are required for general lighting in all types of space, with manual local switches now called for within 6 m of the fitting or twice the height of the luminaire above the floor. Where a space is served by side windows and daylight, Part L asks for the outer row of fittings to be separately switched. Note that no easement is now given for using lighting controls because the calculation tool used to determine the overall BER (Building carbon-dioxide Emission Rate) accounts for their impact. More information is awaited regarding this aspect. Modification is, though, allowed in L2B — but more of that later.

Display lighting undergoes a slight change. Whilst the initial efficacy target of not less than 15 lumens per circuit Watt is retained, lighting controls are introduced. A way of meeting the requirement is to connect the display lighting in dedicated circuits that can be switched off when not required, using time switches. Finally emergency lighting is excluded.

Outside of document L2A, but still within Part L, are overall performance standards for the building. For lighting, installed power density targets are given.

• In offices, industrial and storage spaces, divide the illuminance for the area by 100, then multiply by 3.75 W/m2 per 100 lx.

• For other spaces divide by 100 and multiply by 5.2 W/m2 per 100 lx.

These targets should not be too difficult to meet with existing best practice.

Work in existing non-dwelling buildings — L2B

The new requirement is that when existing buildings with a floor area over 100 m2 undergo major renovation (consequential improvements, an extension, material change of use or material alteration), their energy efficiency should be upgraded.

Any general lighting system with an average lamp efficiency of less than 40 lamp lumens/circuit Watt should be upgraded by either a new luminaire or with improved lighting controls. Otherwise the requirements as for L2A are followed, with the notable exception of lighting controls where, as previously, luminaire control factors can be applied to the overall efficacy rating when an effective lighting control system is installed. However, these factors have been strengthened i.e. 0.9 instead of 0.8 for photocells and PIRs, and 0.85 against 0.75 for the use of both together. Furthermore, a report from a competent person stating that the control system has been properly commissioned is a necessity.

Concluding thoughts

The lighting requirements of ADL1 and 2 are, quite rightly, more stringent than those of the outgoing Part L. Unfortunately, these regulations are not based upon lighting practice, but on seeking to control energy usage. You cannot simply make lighting decisions on a non-people basis, as working conditions also have to be conducive for the occupants to perform efficiently and in comfort. People function better and more happily if the lighting is right. Lighting is, after all, for people and places.

Hugh King is with Thorn Lighting, 3 King George Close, Eastern Avenue West, Romford, Essex RM7 7PP.



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