Turning insight out

The SLL’s guidance on exterior lighting ranges widely in application, from façades and public spaces to roads and workplaces, as Paul Ruffles explains

The 2018 SLL Lighting Handbook has several chapters that address the exterior environment, including external workplaces, architectural lighting, roads and security.

As with interiors, lighting design for the exterior environment is not just about the lux – it’s about where the light goes and how much you use for each surface or part of the scene. Providing the right amount of light just where it is needed, for lighting a task and for effect, avoids unnecessary energy use and possible harmful effects to wildlife and people.

Perhaps the most straightforward chapter is the one on external workplaces. This covers open spaces, such as goods yards, where vehicles and workers must safely coexist, to more localised areas – loading docks, for instance, where vehicles and workers are in proximity.

Some external work spaces are spread over a large area – for example, where forklift trucks are moving around, and the operator needs to see obstacles in their path, as well as read identifying information on the sides of loads that they need to pick from stacks or vehicles.

Other areas are more localised – sets of valves on petrochemical plants, for instance – or are required for detailed maintenance work. As with interior lighting, the designer needs to choose and position luminaires in relation to each task, to provide the required amount of light while avoiding disabling or distracting glare.

The large new chapter on exterior architectural lighting is a visual feast, with many high-quality images demonstrating how to light a range of building types successfully using different techniques. This covers many ways to integrate lighting into façades, as well as the techniques for their full or partial floodlighting.

With a new building, there is scope to integrate the luminaires and their associated wiring into the façade design. This not only makes the design more coherent, but makes it economic to install. With an existing building, integration is more difficult, especially if the building is listed. The chapter offers guidance on many different ways to light an old frontage, from small fittings on windowsills to hiding them between features, and we hope it will encourage people to move away from the ‘throwing light at a building’ school of façade lighting.

The chapter on road lighting is deliberately entitled ‘Roads and urban spaces’ because it covers all aspects of lighting the urban streetscape. Having said that, the guidance on lighting roads and streets is more comprehensive than other similar guidance. Too often, people emphasise the lighting of the traffic parts of our road – the driving surface – while neglecting the pedestrian areas and surrounding buildings, verges and landscape.

As with interiors, the SLL believes the external spaces of our towns and cities should be lit well for people to work in and move through safely while appreciating the lit external environment. Many public squares and parades now integrate lighting into street furniture, such as seating and planters, to provide practical mounting locations within open spaces and flow light over surfaces. There is often a need to provide localised lighting for steps and stairs between areas at different levels.

Security lighting is an interesting topic because it combines a need to understand where the lighting is going in relation to people and cameras covering various features, such as fences and patrol routes. The positioning of lighting in relation to security staff and a possible intruder is important. Ideally, the security staff need to remain invisible or obscured from the view of the intruders, while the intruders need to show up well against their background and any security barriers. The use of directional lighting, differential brightness and, perhaps, semi-silvered glass in windows might assist in achieving this.

The handbook also looks at commissioning and maintenance. It is very important that exterior lighting systems – often subject to wind, rain and freezing conditions – are commissioned correctly and set to work in a fit state. They must also be maintained in a suitable way so they retain their output and, for directional luminaires, their angle of aim.

Some content in the handbook chapters was based on the 2016 SLL Lighting Guide 6 – The Exterior Environment, although it adds much new content. This, in turn, will feed back into an expanded future edition of LG6.

Of course, SLL coverage of external lighting does not stop here. Aspects of exterior lighting are also examined in LG4 on sports lighting – for example, the various levels needed for a range of outdoor sports training and competition, and the more detailed requirements for TV coverage. LG15, on transportation, also covers those exciting external areas around airport terminals, as well as the less spectacular – but more common – areas in and around bus and rail stations.

About the author 
Paul Ruffles is principal at Lighting Design & Technology