A lighting specification: The commercial office environment


Sophie Parry

June 16th, 2020
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Part 1 of this series of articles focused on the basic principles of good lighting when developing a specification or having to make informed purchasing decisions. The first article commenced with the residential environment on the basis that most people live in their own or rented homes and so can relate to lighting and the lit effect in that context. In this article, we’ll switch attention to the commercial office environment.

Internal lighting specifications for offices

Office buildings are constructed in all shapes and sizes and can either be speculative builds, where the ultimate aim is to achieve a landlord/tenant arrangement via shell and core construction, or generic Category A (a.k.a CAT A), both of which require further interior works by the prospective tenant. The other method of construction is bespoke where the client knows exactly what they want and will commission an office building to match their actual needs.

Regardless of the starting point for a project, the specification, location, capacity, and budget for the building will be the key factors in determining what the deliverable. A good quality installed lighting installation may account for 3-4% of the project budget.

Category A speculative projects are common and need an approach that allows for adaptability to enable a tenant to carry out a conversion from CAT A to the desired layout and facilities for their business when adapting the space via a category B fit out.

The aim of the developer should be to create attractive and appropriate CAT A office space to let that includes a generic and scalable lighting installation that can easily be modified by the tenant to suit their business requirement during the tenancy. If required, this installation should allow for the lighting to revert back to the ‘as found’ condition at the end of the tenancy period.

The developer will want to make the lettable space as appealing, and likely as differentiated, as possible when marketing the space to prospective clients. It follows that the lighting installation is an important part of the specification and therefore the informed purchasing phase of the project design.

The CAT A lighting design should consider the following:

  • The use of daylight as part of the lighting deliverable. Natural light is the best form of light and can be modelled at design to reasonably predict the contribution from nature in a way that benefits the space.
  • The quality and coverage of electric lighting to the lettable space on the basis that, at certain times, the office will operate without the benefit of a daylight contribution.
  • Although energy efficiency is important, and there are minimum targets in the Building Regulations for lighting energy usage, it should never be at the expense of the quality of light delivered.
  • Lighting controls are a useful addition to save lighting energy. They’re also used to create different lighting levels or ‘scenes’ to reduce glare or over lighting in meeting and seminar rooms where PCs or large flat screens are used to make presentations or video calls.
  • The use of scalable, modular lighting products that are easy for the prospective tenant to re-position, extend, or add to when carrying out the CAT B works.
  • Confirming the luminaire choice and specification early on in the design phase. Like all projects, the later a change is made to a specification, the more likely there will be additional costs for the client at the final account due.

Choice and specification of office luminaires

This is a critical part of the specification development process and is often based on the aesthetic preference of a client or architect. This decision is often made because they saw luminaires that they liked on a different project or as a result of the samples presented to them for acceptance, usually as a meeting agenda item lasting maybe just a few minutes. Remember also that luminaires have a visual impact on a space when both switched off and when switched on.

All decisions tend to start with an ‘emotive decision’ like this, but this is where big expensive mistakes can be made that could make or break the space, from the occupant’s perspective, when the building is occupied and in use. The way to mitigate this risk is to test by immersive experience. Build a mock up, or temporally install some of the intended luminaires, and then let your colleagues work under the intended light for at least a few days and ask them to confirm whether the experience was a positive one. Did they suffer from any under or over lighting, glare, or any other noticeable side effects that impacted on their wellbeing and productivity in the office environment?

A good lighting manufacturer or supplier will either have:

  • A show room and a guest worker desk zone that could accommodate a small group for a few days to experience the lit effect, or;
  • The manufacturer/supplier should be willing to ‘loan’ a few luminaires so that your electrician can temporally install if the evaluation is to take place at your own premises.

With this process, you can reach a more considered decision on luminaires with the specification, compliance engineering, and budget locked down and ready for construction.

The final consideration is the ongoing support and serviceability of the luminaires. This point is especially pertinent now where clients with early LED-based installations, nearly a decade old now, are beginning to discover that LED luminaires do not last a lifetime. Unlike earlier fluorescent lamp based luminaires, when the lights go dim or fail, there is rarely an LED tube that can be replaced to solve the problem, as used to be the case with fluorescent lighting.

Budget LED luminaires tend to be sealed with no on-site access to serviceable parts and therefore have to be replaced in their entirety. This often means that if one luminaire has failed and requires replacement in an open plan area, the replacement luminaire will likely emit a light different to the original luminaires and look out of place.

For this reason, the specifier should ensure that a competent electrician is able to change spare LED boards and drivers, and that spares will be available for some time after handover to avoid this operational problem.

It follows that later value engineering (VE) should be avoided if possible, as VE decisions are often made on bottom line savings alone and like most things in life, you get what you pay for.

Beyond the office space

In addition to the workstation positions and meeting rooms, there are other areas to consider. Also up for informed consideration are how the entrance and reception areas are lit, as first impressions count. Other areas to consider are the stairs, lobbies, corridors, and W.C’s. All are likely differentiated between the landlords and lettable areas within the building, so they’re likely to be separately sub-metered for landlord to tenant services re-charging.

External lighting

External lighting is also an important consideration. External lighting falls mainly into two categories:

Functional and safety lighting

Roads, car parks, footpaths and entrances all require lighting to specified levels to ensure the safety and wellbeing of staff and visitors, as well as background lighting to support CCTV camera operation. There are British Standards and guidance that make recommendations for lighting levels for these different categories of external space.

Advertising and statement lighting

This can be anything from advertising or corporate signage through to the increasing trend of illuminating the façade of a building to show-case the architecture at night-time and thus create a ‘landmark.’

With all external lighting that goes beyond a few strategically placed functional and discreet wall luminaires, there are planning approvals to be gained, usually granted by the local authority. The reason for this is that, if left unchecked, the rising popularity of such external lighting schemes can cause detrimental ‘light spill’ to neighbouring properties and also contribute to ‘sky glow’. This whole subject of light pollution is governed by urban and rural night time lighting zones that are designed to reduce the unwanted effects of light pollution that effect both humans and, based on recent research, also adversely effects flora and nocturnal fauna.

What’s different about lighting a residential and a commercial project?

In a nutshell, it’s a whole different ball game. Some of the luminaire performance features that were mentioned for residential lighting, such as lumen output, colour temperature, colour rendering, and how we control the lighting are also key performance considerations. External lighting is also subject to the rules of limiting light pollution, but that’s where the similarities end.

Each type of commercial project should be considered as an application when it comes to lighting. The project is lit for a specific task or series of tasks and the requirements for appropriate lighting have been developed over many years, adapting to the changes in technology and energy constraints applied to all other building services.

The net result is that there are best practice design guides for lighting each application, which have usually been written by the industry’s umbrella organisation – i.e. British Council for Offices (BCO) as well as the professional societies such as CIBSE/SLL (Chartered Institute of Building Services Engineers/ Society of Light & Lighting) or the ILP (Institute of Lighting Professionals).

In addition, there may be specification requirements for the lighting to contribute points to BREEAM or WELL certification that need to be taken into account.

The other big difference on commercial lighting projects is the requirement for emergency lighting, which applies to both the landlord and tenant areas.

The thing to note about emergency lighting is that, although it does not add to the project aesthetic and could be considered a ‘grudge’ buy, it is required by law and has to be maintained to be fit for purpose should it be required to operate under emergency conditions. The continued operation of emergency lighting is the legal responsibility of a nominated responsible person who is responsible in law for ensuring the emergency lighting and other life safety-fire safety related items and services are ready for operation at all times during the occupation of the premises, otherwise prosecution for failure to comply is likely. There is recent case history of such prosecutions where upon inspection, emergency lighting has been found to be in disrepair and not deemed fit for purpose.


We’ve reviewed the key considerations for office lighting, but to a certain extent these can also be applied to educational and industrial buildings. As with most things, you get what you pay for. By engaging with experienced lighting professionals, the lit effect should enhance the space, meet all the less obvious compliances, and benefit the people who have to do a productive job of work in the lit environment.

Image credit: iStock.com/serts

About Sophie Parry

Sophie, a qualified electrical engineer of 30 years, has spent much of her career specialising in lighting and currently works for Zumtobel Group providing lighting technical application research, guidance, and training in the UK & Ireland. Sophie is a published author, international speaker, Fellow of the Society of Light & Lighting, and member of SLL’s technical and publications committee.

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