ExclusivesOfficesStandardsTechnologyThe SLL Code for Lighting (2022): Using light to promote health and wellbeing in buildings

The Society of Light and Lighting (SLL) has published an updated Code for Lighting. Published at the very end of last year, the 2022 edition replaces the 2012 version, and reflects the significant changes experienced in the lighting sector over the course of that decade – including the connection between lighting and wellbeing.

The new SLL Code features changes to lighting targets and calculation methodologies, as would be expected. But the revisions also capture an increased understanding of how light and lighting impacts on the health and wellbeing of people.

Lighting a 24-hour society comes at a cost

In our 24-hour society, we can’t escape that living and working around the clock is now commonplace. What is the cost of that, beyond the financial cost of providing lighting installations?

There is a health cost because, in evolutionary terms, the human body was not designed for round-the-clock living. And there is the environmental cost of manufacturing, operating, maintaining and replacing lighting equipment.

The benefits and costs of lighting must be balanced, and the 2022 Code’s recommendations aim to strike that balance. In publishing the updated Code, the SLL acknowledged that: “The basis of energy efficient lighting is to provide the right amount of light, in the right place, at the right time, with the right lighting equipment.”

Lighting can “lift the human spirit” …

…if it is the right quality of lighting. The Code defines ‘bad quality’, ‘indifferent quality’ and ‘good quality’ lighting.

When lighting quality is bad, you can’t quickly and easily see what you need to see. Alternatively – or as well – the lighting installation causes visual discomfort.

Indifferent quality lighting addresses these issues; it could be termed as ‘functional’. The Code is careful to emphasise that providing indifferent quality lighting is an achievement – but that, unlike good quality lighting, it does not lift the human spirit.

Good quality lighting is context-specific

The Code defines a good quality lighting installation as “one that meets the objectives and constraints set by the client and the designer.”

This goes beyond using photometric measures as the only measure of success. It is about the impact that lighting has on “more distant outcomes” – in other words, is the design intent for the specific context achieved?

LEDs are now the dominant light source

A significant driver for updating the Code is the rise of LED lighting. When the 2012 Code was published, LEDs were in their infancy; ten years later, the technology has advanced and LEDs are the dominant light source.

The Code can now acknowledge the discussions that have taken place relating to “lighting metrics, colour rendering, and the spectral content of LED light sources”, as a result of this dominance.

We’re still learning about the non-visual effects of artificial lighting

The adoption of LED lighting has required research into its non-visual effects – how it might support or disrupt our circadian rhythms, for example.

Our relationship with light goes far beyond simple task lighting

The Code is clear that more knowledge is needed to address non-visual impacts with confidence, but it is a stark reminder that our relationship with light goes far beyond simple task lighting.

Lighting designs must include daylight

The evolution of our circadian rhythms has followed the pattern of daylit days and dark nights. Daylight, and an appropriate level of exposure to it, is central to our health and wellbeing.

The revised Code is now aligned with EN 17037, the Europe-wide code of practice for daylight in buildings. As well as illuminance, EN 17037 includes recommendations for glare prevention, sunlight exposure, and assessing the view out of windows. These are all variables not associated with electric lighting, and which require different forms of control to help create a comfortable environment.

In recognition of this, the Code says, “Daylight should appear to users to be dominant in the interior. The control of artificial lighting should ideally relate to the daylight characteristics of the space.”

Light exposure can treat seasonal mood disorders

Although the non-visual aspects of light require greater understanding, one area in which there is no controversy is the treatment of seasonal mood disorders. While the exact mechanisms for these disorders are not well-understood, the Code references the value of light therapy and its effectiveness – especially for winter depression, or seasonal affective disorder (SAD) as it is better known.

Lighting influences safety in many ways

Home and workplace safety is about more than just adequate lighting for the task at hand. There is a positive impact on our health and wellbeing when we feel safe and secure in our environments.

That can range from lighting that helps us to navigate buildings and spaces easily; adequate lighting of common spaces and security lighting; and appropriate emergency lighting and illumination of escape routes should they ever need to be used.

More broadly, the Code also addresses road and street lighting, and its ability to enhance safety and reduce crime.

The environmental cost of lighting extends to its disposal

What happens to electrical lighting installations at the end of their useful life? Designing schemes to reduce the use of artificial lighting – including by incorporating daylighting – prolongs the life of the equipment and reduces the volume of it that needs to be disposed of.

The Code discusses the Waste Electrical and Electronic Equipment (WEEE) Regulations 2013 and how all lighting equipment (with a couple of exceptions) is hazardous waste that has to be disposed of accordingly. For as long as lighting equipment remains part of a linear economy, it is to the benefit of us all to reduce the amount of waste that is generated from it.

Quantitative measures for lighting are still needed

Much of this article has concerned qualitative aspects of light and lighting. It is nevertheless worth pointing out that the Code is a highly technical document and features many metrics and calculation methods designed to assess quantitative targets.

Good quality lighting is something of a fluid concept. Indeed, many buildings might require nothing more than indifferent lighting. Without quantitative targets, however, bad lighting quality is more likely to be the result. The safety and wellbeing of people will therefore be at risk, long before a project might get the chance to enjoy the possibilities that good lighting quality could create.

Interested in the power of lighting and its influence on health and wellbeing? Register for details of Tamlite Lighting’s next one-day Thought Leadership conference, Let’s Talk About Light.  Work in Mind readers are also encouraged to explore Tamlite’s CIBSE Certified CPD Modules – which can be presented in person, or online. 

Or, read more Work in Mind articles about lighting here, including our interview with Ruth Kelly Waskett (a recent President of the SLL) about the power of daylighting.