L of a change

Last month we looked at Approved Documents L1A and L1B; these cover new and existing dwellings respectively. Approved Document L2A covers new buildings other than dwellings, while L2B focuses on work carried out in existing buildings other than dwellings.

Part L2A

General lighting efficacy in office, industrial and storage areas in all building types

Approved Document L2A states that reasonable provision would be to provide lighting with an average initial efficacy of not less than 45 luminaire-lumens/circuit-watt (lm/W) as averaged over the whole area of these types of space in the building.

This is calculated by: (lamp lumens x LOR) summed for all luminaires in the relevant areas of the building, divided by the total circuit-watts for all the luminaires where: lamp lumens is the sum of the average initial (100 hour) lumen output of all the lamp(s) in the luminaire; and LOR is the light output ratio of the luminaire, ie the ratio of the total light output under stated practical conditions to that of the lamp or lamps contained in the luminaire under reference conditions.

This is similar to the provision in the Part L 2002 edition except for the increased efficiency requirement from 40 to 45 lm/W and the removal of the luminaire control factor.

General lighting efficacy in all other types of space

L2A recognises that for lighting systems serving other types of space, it may be appropriate to provide luminaires for which photometric data are not available and/or are lower powered and use less efficient lamps. For such spaces, the requirement would be met if the installed lighting has an average initial (100 hour) lamp plus ballast efficacy of not less than 50 lm/W. This is again a similar approach to the 2002 Part L.

Lighting controls for general lighting in all types of spaces

Lighting controls should be provided so as to avoid unnecessary lighting during the times when daylight levels are adequate or when spaces are unoccupied. For safety reasons, automatically switched lighting systems should be subjected to risk assessment.

Reasonable provision would be local switches in easily accessible positions within each working area or at boundaries between areas and general circulation routes.

The distance on plan from any local switch to any luminaire it controls should generally be not more than six metres, or twice the height of the luminaire above the floor if this is greater. Where a space is a daylit space served by side windows, it would be reasonable for the perimeter row of luminaires to be separately switched.

One way of meeting the requirement would be to follow the recommendations in BRE Digest 478 Selecting lighting controls, 2006. The main differences from the 2002 Part L are that the maximum distance from manual switches to the luminaires they control has been reduced and that there is no control factor.

Display lighting

Reasonable provision for display lighting would be to demonstrate that the installed display lighting has an average initial (100 hour) efficacy of not less than 15 lm/W. The power consumed by any transformers or ballasts should be taken into account. This will rule out GLS lamps but allow most types of tungsten-halogen lamp.

A way of meeting the requirement for controls would be to connect display lighting in dedicated circuits that can be switched off at times when people will not be inspecting exhibits or merchandise or attending entertainment events.

Electrical space heating and hot water heaters

Reasonable provision for the performance of heating and hot water system(s) would be:

• the use of an appliance with an efficiency not less than that recommended for its type in the Non Domestic Heating, Cooling and Ventilation Compliance Guide; and
• the provision of controls that meet the minimum control requirements as given in the Guide for the particular type of appliance and heat distribution system.

Commissioning of heating and hot water systems

The heating and hot water system(s) should be commissioned so that, at completion, the system(s) and their controls are left in the intended working order and can operate efficiently for the purposes of the conservation of fuel and power.

Controls and energy metering

Systems should be provided with appropriate controls to enable the achievement of reasonable standards of energy efficiency in use. In normal circumstances, the following features would be appropriate for lighting, heating, ventilation and air conditioning controls:

• the systems should be subdivided into separate control zones to correspond to each area of the building that has a significantly different solar exposure, or pattern, or type of use; and
• each separate control zone should be capable of independent timing and temperature control and, where appropriate, ventilation and air recirculation rate; and
• the provision of service should respond to the requirements of the space it serves. If both heating and cooling are provided, they should be controlled so as not to operate simultaneously; and
• central plant should only operate as and when the zone systems require it. The default condition should be off.

Reasonable provision for energy meters would be to install energy metering systems that enable at least 90% of the estimated annual energy consumption of each fuel to be assigned to the various end-use categories (heating, lighting, etc). Detailed guidance on how this can be achieved is given in CIBSE TM 39.

Also the performance of any low and zero carbon (LZC) energy source systems are to be separately monitored and in buildings with a total useful floor area greater than 1000m2, there must be automatic meter reading and data collection.

The owner of the building should be provided with sufficient information about the building, the fixed building services and their maintenance requirements so that the building can be operated in such a manner as to use no more fuel and power than is reasonable in the circumstances.

A way of showing compliance would be to produce information following the guidance in CIBSE TM 31 Building logbook toolkit.

Part L2B

There are exclusions to what counts as an existing building. For example, where the proposed extension has a total floor area that is both greater than 100 m2 and greater than 25% of the floor area of the existing building, then the work should be regarded as in a new building and Approved Document L2A applies.

Where there is a material change of use, the building or part of a building should comply with the applicable requirements of various parts of Schedule 1, including Part L.

Regulation 17 requires “consequential improvements” to improve the energy efficiency of the whole building when there is an extension or alteration of over 100 m2. For lighting, it is considered that reasonable provision for consequential improvements would be, for any general lighting system serving an area greater than 100m2 and which has an average lamp efficacy of less than 40 lm/W (ie below the standard in the 2002 Part L), to upgrade it by the provision of new luminaires or improved controls.

General lighting

The efficiency criteria are generally the same as the “fall-back” criteria for new buildings, ie 45 lm/W for offices, industrial and storage areas, 50 lm/W in other types of space, and 15 lamp lumens per circuit-watt for display lighting along with requirements for controls, with the additions of a control factor.

Unlike the provisions for new buildings, those in Approved Document L2B still include a controls factor defined as the factor applicable when automatic controls substantially reduce the power consumption of the luminaire when electric light is not required.

Requirements for electrical space heating, hot water heaters and controls and energy metering are similar to L2A requirements, as are the requirements for commissioning and building log books.