09 June 2017

The modern office developments and office refurbishments need to comply with Building Regulations. These are minimum standards for design, construction and alteration for literally every commercial building. It's not just the larger projects with architects and consultants involved right from the initial design stages, but also commercial landlords and commercial end users looking to fit out their offices. 


These Building Regulations have some core elements valid for the whole of UK, but there are now versions solely for England, Wales, Scotland and Northern Ireland.There are several regulations for new and existing buildings to achieve high energy efficient projects and the whole subject can be quite overwhelming. In this article, we will focus on Building Regulations relating to commercial office market.

When it comes to lighting, the focus is still on luminaire performancewith an option to include lighting controls factors. As a way to measure the actual performance of a scheme, Leni was brought in during April 2014. It governs the introduction of lighting into new premises. Part L Building Regulations 2013 only relate to England and are no longer applicable to Wales. They apply to most new building and alterations and are a legal requirements.

LENI (Lighting energy numeric indicator)

This is an alternative means of demonstrating the compliance of lighting systems. It means that compliance can now be demonstrated either by meeting the recommended minimum standards for efficacy and building controls, or by meeting the recommended minimum standards for LENI. The calculation methodology for LENI is set out in the Non-domestic Building Services Compliance Guide. LENI indicates the efficiency of the whole lighting installation (including controls) and is expressed in energy used per square metre. The LENI of a build must not exceed the prescribed limit for a given illuminance and the number of hours per year the lighting will be required.


LENI is worked out on the level of illuminance in an area and the number of hours per year that lighting is required. The calculation accounts for:

  •  Energy used by any lighting control systems.
  •  The total power of the lighting in watts.
  •  Energy saved by automatic control systems, both switching off when no one is around and dimming when there is a degree of natural light.
  • The ability of lighting to retain its efficiency.

Put simply, the LENI is the sum of energy used divided by the area. The industry supports this measure and there will be some changes in the 2016 edition. For more details on levels of illumination, check the Table 44.

#1 | Guidance




LG7 is the successor of LG3 Lighting guide: The Visual Environment for Display Screen Use. First published in 1989, providing advice for lighting offices that introduced computers. The fluorescent luminaires equipped with opal diffusers or prismatic controllers worked fine for paper based environment, but as soon as the computers with curved glass screens started appearing in offices, this glare became a serious issue. LG3 categorised the office environment in to 3 types and identified suitable approaches to lighting design for each one. With the arrival of flat screens and portable devices, the LG3 became irrelevant and The Society of Light and Lighting (SLL) has formally withdrawn the LG3 from use.

The Society of Light and Lighting (SLL), part of the CIBSE (Chartered Institution of Building Services Engineers) publishes a raft of lighting guidance which reflects the relevant European Standards. It covers the recommended illumination levels for task, but also looks at the application of light. The SLL Code for Lighting (2012) covers all the technical aspects of the application of light, including the all-important numbers. It explains, that these numbers are not set in stone, but this is often overlooked in specifications that stick to the numbers without taking the design or needs of people into consideration.

There are chapters that cover the main design elements for each application, providing its own guide for the lighting of offices - Lighting Guide 7 (LG7).

The purpose of this guide is not only to ensure adequate levels of lighting but to also provide a stimulating environment for office workers. LG7 recognises that there are different lighting environments, requiring various approaches (e.g. open plan, cellular and deep plan) and the emergence of new technologies, such as tablets, smartphones and touchscreen computers.

LG7 also informs on how best to select luminaires, lights sources and their controls (i.e. ability to dim and setup controls to limit energy waste), considering the needs of employees to create a tailored approach. This means that lighting is utilised in the interior design process to bring out varying tones across a space. Other factors considered include; the flexibility of the workspace (i.e. will it be necessary to move furniture), are there heritage features to be considered, requirements in terms of light colour and will emergency lighting be required.

Cylindrical illumination (distribution of light within various areas of the workspace) is also covered. It is recommended that the task area (e.g. desk area worked in) should be between 300 to 500 lux and 1200 to 1600 mm above floor level should be lit to 150 lux.


Colour used in an office can affect the experience of users. Warmer colours, such as 2700K (warm white), will tend to be beneficial in creating a more relaxed environment, while 4000K (cool white) keeps employees more alert. Extremely cold light sources nearer to 6000 or 7000 K can distort colour appearance or give the occupants of the room an unhealthy pallor.

All walls and ceilings should be illuminated. An employee needs to be able to look away into the distance to avoid eye strain. The best scenario here is that they can look outside but if not, there should be a distance to look into, and the walls and ceiling within this view should be lit to a similar level to the task area (see fig.2 below).

Glare is an issue that occurs whenever one part of an interior is much brighter than the general brightness of the interior. The most common sources of excessive brightness are luminaires and windows, seen directly or by reflection. Glare can have two effects: it can impair vision, in which case it is called disability glare, and it can cause discomfort, in which case it is called discomfort glare. Disability glare and discomfort glare can occur simultaneously or separately.

Daylight should be the key component of the design and the best practice for utilising daylight in conjunction with having dimming settings is also covered to allow for energy saving and improved well-being.

Further to this, the CIBSE also recommends the following lighting levels (In Lux) for other work places.

For further information on LG7 please refer to CIBSE’s website here.



Published by CIBSE, this guideline focuses on designing with daylight in mind, addressing the issues of aesthetics and building physics. The format of this guide follows the design process, beginning with outline considerations of form and orientation and leading on to the more detailed aspects of designing the building envelope to admit or to filter natural light through different shading systems. It also deals with the multitude of different visualisation techniques that allow the design team to explore the appearance of design solutions. In addition, it provides a guide to more detailed resource material.

The recently published guide on designing for daylight supersedes the previous edition CIBSE Lighting Guide LG10: Daylighting and window design, which was published in 1999, and which is now withdrawn.

This guide document aims primarily at new design work, however, much of the guidance will be applicable to refurbishment projects. The guidance in this document is written for buildings located within the UK, but can be applied at other locations when local regulations are respected. The full version of LG10/2014 can be purchased here.


#2 | Regulations


BS EN 12464-1:2011

BS EN 12464 is a standard that specifies lighting requirements for offices (indoor work places). The lighting requirements here are dictated by three basic human needs; Visual comfort (lighting should give workers a feeling of well-being and therefore contribute to their productiveness), visual performance (workers must be able to fulfil visual tasks under difficult circumstances and for longer durations of time) and lighting should enable all work to be carried out safely.

BSI (British Standards Institution) sets out the standards for the lighting of indoor (BS EN 12464-1) and outdoor (BS EN 12464-2) work places in accordance to the European Standard. The standard's aim is to encourage designers to plan and introduce appropriate lighting controls for regular lighting layouts and buildings. It doesn't prescribe any specific solutions, nor it restricts from exploring new techniques or use of innovative lighting equipment.

Part 1 of BS EN 12464 specifies requirements for lighting in main offices areas and the associated areas in terms of quantity and quality of lighting. In addition recommendations are given for good lighting practice.

There are some significant changes to the previous version of the standard, mainly encouraging to consider all light sources, including natural light, not just electric lighting. The use of day light is also recognised as an important contribution to energy saving. Specification of the minimum illuminance of walls and ceilings is included to increase brightness of a room.

The standard looks into glare and shielding against it, colour aspects and appearance, colour rendering, maintenance factor and energy efficiency requirements, to name just a few. To purchase the full version of BS EN 12464 standards, visit BSI here.

BCO Guide to Lighting

The British Council for Offices (BCO) is the leading forum for the discussion and debate of all issues around the office sector. The Guide to Lighting aims to provide best practice and professional advice on how to specify good office lighting. It recognises the fast pace and dramatic changes the world of lighting is going through.

The main message is to use daylight effectively and use the artificial lighting only where and when required. The aim of this objective is to reduce the amount of energy consumed by lighting.

The new Guide is split into 3 sections: The first talks about the daylight and energy use; The second one looks at principles of lighting practice; and the third one gives examples and guidance for lighting of CatA and CatB office fitout.

The Guide to lighting is aligned with the latest guidance from the British Standards Institution (BS EN 12464-1) and the Society of Light and Lighting. The latest version (2013) could be purchased here.


Part L

Part L is part of the building regulations issued by the Secretary of State, laying down measures to conserve fuel and power (of which lighting is an aspect). This regulation will need to be adhered to when extending a building or when replacing existing lighting systems.

Within the regulations certain sections relate to; L1A - New Dwellings, L1B - Existing Dwellings, L2A - New buildings other than dwellings, L2B - Existing buildings other than dwellings.

L1A and L1B refer to the Domestic building compliance guide, which you can see here. L2A and L2B refer to the Non-domestic building compliance guide which you can see here.

The L2A document took effect on 6th of April 2014 and is for use in England.

In all new dwellings, 75% of the fixed internal light fittings must have a minimum of 45 lamp lumens per watt and must have a greater output than 400 lamp lumens (in order to be counted). All lights emitting less than this (i.e. bedside lamps) do not need to be considered during fitting.

In the case of external lighting at new dwellings, products need to be under 100 watts and be controlled by light sensors so that they do not waste energy in daylight hours of sufficient light. Alternately they may have a light efficiency of over 45 lumens per Watt and again should be controlled by a light sensor (or manually controlled).

For non-domestic builds (highlighted in L2A), the sum of all general light fittings in offices, industrial and storage areas need to be a mean of 60 luminaire lumens per circuit watt.

For general lighting in ‘other’ types of space, the total of all fittings should have an average efficiency of 60 lamp lumens per watt and 22 lamp lumens per watt for all display lighting (However having lighting controls might allow builds to have a lower average output).

Certain builds are exempt from these regulations, including listed buildings, monuments and places of worship (we recommend you make enquiries if you are uncertain what your obligations are).


BS 5266

Part 1 of BS 5266, published by BSI Standard Limited, under licence from The British Standards Institution, came to effect on 31st May 2016. It supersedes BS 5266-1:2011 and aims to promote wider understanding of different types of emergency lighting systems and give guidance on their correct application.

The purpose of the guide is to encourage uniformity in implementation, to ensure safety should normal lighting fail and to promote understanding of the diverse types of emergency lighting system that may be used in varying types of premises.

This guide targets Lighting engineers and electrical contractors who must protect building occupants from the hazards identified in risk assessments. It also intended to give owners and landlords reassurance that they are meeting their legal obligations.

There are several factors that need to be considered in the design, including installation and wiring of electrical emergency escape lighting systems to provide the lighting performance needed for safe movement of people if normal lighting should fail. For example, generator systems should have back-up battery capable of lasting for an hour (if they do not produce emergency lighting at 50% within 5 seconds and at full power within 60 seconds).

Also, covered in the guide is the required luminance of escape signs (which can either be lit internally and externally) and the fact that they must be visible based on the direction in which occupants are looking in the case of emergency (i.e. not on a ceiling or at an oblique angle).

Illuminance requirements are set out in detail for three major class of areas and specific rooms (the location of luminaires for ‘points of emphasis’ are also detailed i.e. Stairs and near Firefighting equipment) -

You will also find information relating to the spacing of luminaires, with escape routes needing to have lights close enough to provide 1 Lux across the entire route and open areas needing to provide 0.5 Lux. For more information on further aspects of the BS5266-1, please refer directly to the guide.


Lighting Regulations for Health and Safety

The Government’s Workplace (Health, Safety & Welfare) Regulations (WHSWR) require that all organisations must ensure that all parts of the workplace (internal and external) are adequately lit. It only covers the health and safety aspects of lighting for people in the workplace rather than the creation of pleasant or appropriate lighting environments. Both ambient and background lighting must be utilised to maintain safe working areas and sufficient lighting at machinery and workstations (which might require higher levels of lighting).

Further to this;

  • Lighting as far as possible should be provided naturally (windows and other sources of natural light should be regularly cleaned).
  • Sufficient emergency lighting should be provided in the event of the failure of artificial lighting (this should be independently powered from the main light source). Emergency lighting is essential in environments where when artificial light fails the lack of light presents a significant health risk.
  • Lighting should not cause glare and be suitably distributed and maintained. This is to ensure there is no visual fatigue or eyestrain for employees.
  • It is the responsibility of the employer to ensure that all light regulating devices are maintained and that they do not become obscured by any objects in the workplace.
  • Should work equipment be used away from the site by an employee, it is the responsibility of the employer to provide sufficient lighting.
  • All previous requirements must be factored in any risk assessment by the employer.


HSG38 also gives recommended illuminance levels, these are split into 5 categories ranging from 20 lux for circulation areas to 500 lux in drawing offices. It also gives the minimum levels deemed acceptable.

Quality of light necessary by illuminance (taken directly from HSE Guidance Notes HS(G)38: Lighting at Work) in more detail:

(a) Only safety has been considered, because no perception of detail is needed and visual fatigue is unlikely. However, where it is necessary to see detail to recognise a hazard or where error in performing the task could put someone else at risk, for safety purposes as well as to avoid visual fatigue, the figure needs to be increased to that for work requiring the perception of detail. The CIBSE Code for lighting 4 gives more information and recommendations based on scientific knowledge, practical experience, technical feasibility and economic reality.

(b) The purpose is to avoid visual fatigue; the illuminances will be adequate for safety purposes

(c) The purpose is to avoid visual fatigue; the illuminances will be adequate for safety purposes

(d) The purpose is to avoid visual fatigue; the illuminances will be adequate for safety purposes For further details please refer to the publication of Lighting at Work, accessible here.

Please be aware that building regulations are often changing so you will need to refer to the up to date publications in your location.