All contributions are the responsibility of the author, and do not necessarily reflect the views of the society. All contributions are personal, except where attributed to an organisation represented by the author.
COPY DATE FOR LL1 2025 IS 13 NOVEMBER
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FROM THE EDITOR
We've come a long way in the past 30 years in our appreciation of the relationship between light and human beings. Both the biological and psychological interconnections are beyond dispute, although still in need of considerable research, as we know.
While we are at the early stages of comprehending what is clearly a fundamental and universal relationship, especially the effect of light on our circadian system, we are also beginning to explore more specialised areas, including the effect of lighting on particular conditions such as dementia, neurodiversity or visual impairment.
Creative director and light artist Frankie Boyle, who has produced a special installation for Light 24 at London's Building Design Centre this month, offers an insight into just how significant light can be for the neurodiverse (Colourful Language, p11).
Diagnosed with developmental learning disorder (DLD) and dyslexia at the age of seven, Boyle has experienced great difficulty with
communicating. However, she explains, she always understood the language of light. 'Light and human behaviour were definitely the first languages I understood,' she says.
As an artist, she has explored light’s dynamic effects on mental health and human behaviour, and advocates for the therapeutic potential of immersive art.
Notably the conference programme at Light2Perform at London's ExCeL this month will include sessions on two specialised areas, lighting for neurodiversity and visual impairment. As with illuminating the natural environment (see Sept/Oct issue), one light does not fit all.
CURRENT SLL LIGHTING GUIDES
SLL Lighting Guide 0: Introduction to Light and Lighting (2017)
SLL Lighting Guide 1: The Industrial Environment (2018)
SLL Lighting Guide 2: Lighting for Healthcare Premises (2019)
SLL Lighting Guide 4: Sports Lighting (2023)
SLL Lighting Guide 5: Lighting for Education (2011)
SLL Lighting Guide 6: The Exterior Environment (2016)
SLL Lighting Guide 7: Office Lighting (2023)
SLL Lighting Guide 8: Lighting for Museums and Galleries (2021)
SLL Lighting Guide 9: Lighting for Communal Residential Buildings (2022)
SLL Lighting Guide 10: Daylighting – a guide for designers (2014)
SLL Lighting Guide 11: Surface Reflectance and Colour (2001)
SLL Lighting Guide 12: Emergency Lighting (2022)
SLL Lighting Guide 13: Places of Worship (2018)
SLL Lighting Guide 14: Control of Electric Lighting (2023)
SLL Lighting Guide 15: Transport Buildings (2017)
SLL Lighting Guide 16: Lighting for Stairs (2017)
SLL Lighting Guide 17: Lighting for Retail Premises (2018)
SLL Lighting Guide 18: Lighting for Licensed Premises (2018)
SLL Lighting Guide 19: Lighting for Extreme Conditions (2019)
SLL Lighting Guide 20: Lighting and Facilities Management (2020)
SLL Lighting Guide 21: Protecting the Night-time Environment (2021)
SLL Lighting Guide 22: Lighting for Control Rooms (2022)
Guide to Limiting Obtrusive Light (2012) Code for Lighting (2022)
Commissioning Code L (2018)
SLL Lighting Handbook (2018)
CIBSE TM66: Creating a Circular Economy in the Lighting Industry (2021)
CIBSE TM65.2: Embodied Carbon in Building Services – Lighting (2023)
FROM THE SECRETARY
It’s been a busy return after the summer break. The society has hosted webinars, supported conferences and attended exhibitions, and is currently preparing for more events.
The online event EPD, or Go Home? with Irene Mazzei, sustainability lead at Stoane Lighting, discussed life-cycle assessment (LCA) and environmental product declarations (EPD). The recording is now available (see box).
Events have been both national and local. The ICEL Emergency Lighting conference, which the SLL partnered, was excellent and also extremely informative.
Alex Draper, SLL regional lighting representative for the East Midlands, hosted a presentation with Tridonic on emergency lighting incorporating DALI2 and wireless technology. The recording is now also available to view.
The SLL North West and Scotland regions hosted presentations and discussions on museums and conservation in early October. Mark Sutton-Vane, Jim Ashley-Down and John Harris spoke at the first event, with Kevan Shaw and Dave Hollingsbee speaking in Scotland. Thanks to SLL Sustaining Members ERCO and Stoane Lighting for supporting the events, and SLL regional lighting representative Giorgos Kourtelis and Lisa Sutherland for organising them. Meanwhile the South West region hosted Commercial Lighting Controls with Luceco Lighting. Thanks to the society's regional lighting representatives Jennifer Neal and Nathan Wright for organising the event.
Also in October, the SLL exhibited and had a speaker slot at the Healthcare Estates Conference, Exhibition and Awards at Manchester Central. The SLL speakers were Nicholas Bukorovic (lead author LG02: Lighting for Healthcare Premises) and David Mooney (lead author of LG12: Emergency Lighting).
In what was a busy month, the society also supported the Recolight Circular Lighting Live Conference and Exhibition, while a sell-out SLL Ready Steady Light, with Rose Bruford College and the IALD, followed in mid-October. We will have an article on RSL in the next issue, but details of winners are now on the SLL website.
In a new departure, this year's SLL Young Lighter Final took place simultaneously in Edinburgh, Leeds, Oxford and London towards the end of October. The winner will be officially announced at Light2Perform (see below) on 13 November.
• To view the online event EPD, or Go Home?: www.youtube.com/watch? v=pS4kWYoCADI
• To watch Emergency Lighting Incorporating DALI2 and Wireless Technology: https://youtu.be/EXJb03ySch8
• For more details of the Light2Perform conference programme: www.build2perform.co.uk/slllight2perform
Rounding off a very eventful month, David Battersby hosted The Basics of Lighting Design and Controls at the Royal Armouries, Leeds. Speakers were Nigel Monaghan of Luminous Solutions, Stephen Marley of Helvar, and Craig Wood of Urbis Schreder.
A reminder that Light2Perform 24 returns on 13-14November at ExCeL, London. We are joined by the ILP, LIA and Recolight, and the conference will take place on 13November. The following week, 20-21November, SLL will again be at LiGHT 24, this time in the Associations Lounge at the Building Design Centre, London. Jeff Shaw, lead author of the upcoming LG23: Lighting for Creativity and Compliance, will present a preview of what will be a brand new publication.
We're also again looking forward to Light+Intelligent Building Middle East, from 1416January, at the Dubai World Trade Centre. We will be exhibiting, and SLL president Dan Lister will be a speaker and panellist. Ready Steady Light Dubai returns and registration for the competition will be available soon.
The SLL will exhibit for the first time at the Workspace Design show on 26-27 February, again at the Building Design Centre. SLL members will be taking part in the lighting panel discussion at the show.
Finally, we welcome new SLL UAE regional lighting representatives, Neethu Susan George and Chris Carr. We look forward to working with them.
UNEQUAL TO THE TASK KitCuttleontherelationshipbetween lightingpracticeandlightingpurpose
COVER: The latest installation by Dutch artist and innovator Daan Roosegarde honours the rich mining history of Genk in east Belgium. Lichtsporen (Traces) are light-sensitive stones 'that explore the earth’s hidden energy'
NEW APPROACH FOR YOUNG LIGHTER FINAL
For the first time the SLL Young Lighter 24 final took place in four locations simultaneously, in Edinburgh, Leeds, Oxford and London, towards the end of October. The winner will be officially announced in mid-November.
The four finalists gave presentations on a wide range of lighting topics. Samuel Walker of OBS Lighting Consultants (second left) examined the interactive educational platform Observe, while Jess Keates of Hoare Lee (second from right) gave a paper titled Beyond the Line, which looked at applying our understanding of the effects of spatial frequency and contrast on visual discomfort.
Kate Turley of Chroma Lighting (far left) discussed how to support the wellbeing of people living with dementia, focusing on a tailored dynamic lighting and sensing paradigm. Tammy Julleekeea of dpa lighting consultants (far right) explored ways of protecting sub-surface eco systems with her paper Re-illuminating the waters.
'The quality of submissions, the novel ideas and the passion have been outstanding, and I thank all the candidates who entered,' said Kristina Allison, SLL president elect and chair of this year's Young Lighter judging panel.
Each presentation was broadcast to the other venues, with audiences also given the opportunity to take part in the voting.
The competition has run for 29 years and is for anyone under 30 years of age who is interested in light and lighting, regardless of background or education. The winner is awarded the title of SLL Young Lighter and a cash prize of £1000. Each finalist also receives a cash prize.
The winner of SLL Young Lighter 2024 will be announced on 13 November at the Light2Perform conference at London's ExCeL
ON THE LIGHTER SIDE…
Among a range of left-field ideas at the Material Matters show in London in September were lights made of wheatgrass roots. Former underwater photographer Zena Holloway founded Rootfull after seeing the effects of plastic pollution in the oceans and was inspired by the tangled root system of a willow tree in her local river.
The shoots of the plant grow to 20cm over 12 days on beeswax templates, with the roots binding below to form a naturally woven structure. It’s then harvested, washed, dried and
treated with natural ingredients.
'The entire process incorporates organic and locally sourced materials,' says Holloway. 'Water is recycled from runoff, and any excess shoot or seed is repurposed as animal fodder, leaving no waste behind.' www.rootfull.com/
NET ZERO STANDARD
A pilot version of the UK’s first cross-industry standard for net zero carbon aligned buildings was launched in September.
CIBSE is among the organisations –including RIBA, the BRE and the Carbon Trust – which have joined forces to champion the initiative.
The UK Net Zero Carbon Buildings Standard is a free-to-access technical standard designed to enable the construction industry to prove that built assets align with the UK’s carbon and energy budgets.
'Until now there has been no single, agreed methodology for defining what net zero carbon means for buildings in the UK,' says CIBSE. 'Consequently, the area has been rife with spurious claims around the topic. The standard provides a set of consistent rules to create a level playing field.'
The pilot version contains technical details on how a building should meet the standard, including what limits and targets it needs to meet, the technical evidence needed to demonstrate this, and how it should be reported.
It has been developed and agreed through collaboration between built environment organisations and industry leaders including architects, engineers and carbon assessors. More than 350 experts supported the technical steering group (TSG) during the standard’s development phase.
'The standard has been created not just using industry data on what is achievable, but also cross-referencing this with top-down modelling of what is needed to decarbonise our industry in line with 1.5 degrees C aligned carbon and energy budgets,' said Katie Clemence-Jackson, TSG chair. 'It covers all the major building sectors, as well as both new and existing buildings.'
A pilot testing programme will be launched shortly to glean feedback on applying the process to real projects. To download the pilot version of the UK Net Zero Carbon Buildings Standard: www.nzcbuildings.co.uk/
When electric lighting was being introduced in the early years of the last century, the ability to perform difficult visual tasks was a serious constraint on workers’ productivity, particularly during winter months. This led to the prime purpose of electric lighting being seen as a way of maintaining optimal visual performance in workplaces by providing task illuminance that was matched to visual task difficulty.
The development of procedures to predict and verify illuminance on desktops and workbenches led to confidence that lighting the horizontal work plane was the essential role of lighting practice.
As understanding of visual performance has developed, other ways of overcoming visual performance difficulties have emerged. Examples abound, ranging from screen-based tasks to laser printers and barcode readers, some of which have made the visual tasks easier, and some of which have eliminated the need for them. For the few visually demanding activities that have, so far, withstood change, such as surgery and jewellery making, specialised lighting solutions have been developed which are invariably restricted to the immediate task area.
Meanwhile, lighting standards dealing with workplaces have simply maintained the schedules of task illuminance that evolved during the era of typewriters and carbon copies. Consider the computer screen: it can readily be demonstrated that increasing illuminance on the screen reduces task visibility, so by continuing to
deliver task illuminance on to the horizontal plane, current office lighting practice leaves the actual task plane relatively unlit. There are striking mismatches between the stated aims of the lighting standards and office lighting practice.
Recently, signs of change have emerged. The latest update of the widely referred to indoor lighting standard, EN 12464-1:2022,1 specifies that illuminance values be provided uniformly over 'task or activity areas', but unlike its predecessors, it specifies minimum mean cylindrical illuminance values for 'visual communication and recognition of objects' and minimum average wall and ceiling illuminances to ensure 'room brightness'. In this way, the standard identifies the provision of luminous environments that generate room brightness, support visual communication, and enable recognition of objects as being objectives that indoor lighting should deliver.
This leads to a changed understanding of the purpose of lighting and changed priorities for providing it. Whenever lighting is to be provided
'There are striking mismatches between the stated aims of the lighting standards and office lighting practice'
for an indoor location, there is a need to provide for these ‘luminous environment’ objectives, and this should be seen as a fundamental lighting design objective.
However, the flux level of the luminous environment is an influential factor as it determines the extent to which the lighting may generate visual stimulation, or encourage relaxation, or provide for something in between, and providing an appropriate stimulus level for an application determines the overall quantity of light to be provided within the space. This is to be seen as the first priority for lighting, after which attention may be given to determining the spatial and spectral distributions of the lighting. These secondary priorities are determined by objectives specific to the application, such as visual performance, or creating a distribution of visual emphasis, or achieving efficient flux utilisation. A rational approach to the provision of a lighting scheme must start from an understanding of its purpose.
SPATIAL BRIGHTNESS AS A BASIS FOR ALL INDOOR LIGHTING
Another sign of change is that recently the CIE has defined spatial brightness as an 'attribute of a visual perception according to which a luminous environment appears to contain more or less light',2 and it should be noted that this is distinctly different from the earlier definition of brightness which was concerned with the appearance of individual elements within a scene.
Spatial brightness refers to a prime
influence of lighting on peoples’ visual response to a lit space, which concerns the crucial design issue, 'how brightly lit (or how dimly lit) does this space appear?'
Researchers at the Technological University of Dublin have employed a seven-point scale of spatial brightness ranging from ‘SB-1 Very dimly lit’ to ‘SB-7 Very brightly lit’ to relate peoples’ assessments of spatial brightness to ambient illuminance. This relationship is shown in Figure 1.
I have previously proposed that ambient illuminance be defined as ‘the average density (lm/sqm) of indirect luminous flux within an enclosed space’,4,5 and that a suitable metric for specifying ambient illuminance would be mean room surface exitance (MRSE).5 Table 1 sets out values of MRSE associated with a range of perceptions of spatial brightness, enabling a practitioner to choose a spatial brightness level for a specific application and to specify it by an MRSE value. Furthermore, this SB/MRSE relationship would enable regulators to specify minimum MRSE values for categories of indoor locations in lighting standards based on a perceived adequacy of illumination (PAI) criterion.
There is a need for more research in 'real' situations before a SB/MRSE relationship can be confidently adopted for general lighting practice, but nonetheless some practising lighting designers are currently making use of the lighting design objectives (LiDOs) procedure6 for developing lighting solutions.
This procedure employs a spreadsheet that guides a practitioner who has chosen a combination of lighting design objectives for a specific application through a process that leads to a direct flux distribution (DFD). This provides a specification of the required photometric performance characteristics for a lighting installation to provide the chosen combination of LiDOs. It is hoped that in due course lighting standards will change from prescribing minimum
maintained illuminance levels on task planes to MRSE values for lighting indoor spaces.
The extent to which the century-old concept of the horizontal working plane is ingrained into how lighting practitioners think about what they are doing is revealed by the language they use. Downlighting is described as ‘direct’ lighting because it delivers flux directly on to the horizontal working plane and is, therefore, an eminently efficient way of illuminating a light meter located on that plane.
Uplighting is described as ‘indirect’ lighting and is rated as relatively inefficient, although it may be opted for where a pleasant appearance is required and efficiency is not a concern.
However, all of that thinking changes when, instead of providing illuminance over the
horizontal working plane, the aim is to light a whole space as shown in Figure 2. Then, every lumen emitted by the luminaires is incident –directly – on to a room surface. At every point of incidence, first reflected flux (FRF) is generated and the sum of these FRF values and all the subsequent interreflections comprises the indirect flux field, which is the luminous flux that fills the space and provides for perception of the surrounding surfaces of the room and the objects within it.
The average value of the indirect flux field is the ambient illuminance, which may be seen as the prime determinant of the perception of spatial brightness within a space. Mean room surface exitance is a convenient metric for specifying ambient illuminance.
⊳ Fig 1: spatial brightness (SB) as a function of mean room surface exitance (MRSE), due to Durante and Kelly.3 Descriptors of the seven steps of SB are shown in Table 1
� Table 1: the seven-point scale of spatial brightness related to ambient illuminance
� Fig 2: spatial brightness is being provided effectively and efficiently to supplement the daylight by luminaire flux being directed on to a high-reflectance room surface. Efficient generation of first reflected flux is crucial for efficient flux utilisation to provide ambient illuminance
LIGHTING DESIGN OBJECTIVES AND ILLUMINATION DIVERSITY
Once the spatial brightness of a space has been decided, the next step is to devise the distribution of the direct flux field. For this, the crucial question is, 'Are there any objects or surfaces that would benefit from being given visual emphasis?'
While there are many reasons why lightingimparted visual emphasis might be beneficial, it often happens that there are spaces in a project for which all that is wanted is that the space appears adequately lit for whatever purpose it serves – in which case the answer to the question would be 'No'. We will start with that simple situation.
More research of the perceived adequacy of illumination (PAI) criterion for different applications would enable levels of spatial brightness assessed as appropriate for categories of indoor locations to be specified by MRSE values and become the principal metric for specifying minimum maintained lighting conditions in lighting standards.
Table 2 shows a tentative proposal based on three ranges of general lighting practice, each centred on one of the steps of the spatial brightness scale and specified by the minimum SB value of the range. It is speculated that the midrange of general lighting practice (in other words, SB-3.5 – 4.5) would actually apply for quite a broad range of indoor locations for which lighting is not required to do anything more (or anything less) than make the space and its contents
readily visible and to appear adequately lit.
This would leave scope for an upper-range for locations where visual stimulation due to a more brightly lit appearance is aimed for, such as retail stores or office workspaces, and alternatively, for a lower-range for locations where relaxing effects are aimed for, such as waiting rooms and lounge areas. In the absence of sufficient research to enable reliable use of MRSE values for specifying PAI, this proposal is offered as a reasonable basis for considering how such criteria might operate.
So, if practitioners were to specify lighting quantities in terms of mean room surface exitance instead of working plane task illuminance, in what ways would that influence lighting practice?
The indirect/direct flux ratio (IDFR) serves as
⊳ Table 2: proposed minimum MRSE levels to satisfy the perceived adequacy of illumination (PAI) criterion for three ranges of general lighting practice
the metric of flux utilisation for generating an indirect field, enabling practitioners to compare how efficiently alternative distributions of direct flux produce spatial brightness. Figure 3 compares how effectively typical uplighting and downlighting installations in rooms with conventional ceiling/wall/floor reflectance distributions generate ambient illuminance. The differences of IDFR can be substantial.
Achieving high values of IDFR involves selecting high reflectance target surfaces to receive direct flux, and Figure 2 shows an example of efficient flux utilisation for generating ambient illuminance. However, at this point, considerations other than flux utilance can be expected to come into focus.
The LiDOs spreadsheet enables users to compare IDFR values for alternative solutions.
ILLUMINATION HIERARCHY AND VISUAL EMPHASIS
⊳ Fig 3: a comparison of indirect/direct flux ratio values for an empty 100sqm room with five ceiling/walls/ floor reflectance combinations. Both the downlight and uplight installations deliver 18 per cent of their flux on to the walls and the remaining 82 per cent on to either the floor or the ceiling
If the question, 'Are there any objects or surfaces that would benefit from being given visual emphasis?' evokes a 'Yes' answer, another level of lighting opportunities becomes available. There may be many possible reasons for selecting surfaces or objects in a room for visual emphasis. In a workplace, it might be because there are identifiable visual tasks with specific lighting requirements; in a retail space it would be to draw attention to the merchandise; in a museum, it is likely to be to provide for the individual viewing requirements for specific exhibits; in a circulation space, it might be to guide movement; and in an industrial location, it could be to reveal safety hazards.
Instead of the selection of target surfaces to receive direct flux being directed towards achieving efficient flux utilisation as described in the previous section, target surfaces are selected
� Fig 4: in this retail display area, room surfaces are washed with light to generate a moderate level of spatial brightness, while lighting focused on merchandise displays builds an illumination hierarchy that creates a planned distribution of visual emphasis
to achieve distributions of visual emphasis These are specified by allocating a target/ambient illuminance ratio (TAIR) value from Table 3 to each target surface.
The ratings of visual emphasis given in Table 3 are based on experience rather than research, but there are currently several lighting design practices making use of this scale and, so far, feedback indicates that it works satisfactorily. The LiDOs spreadsheet is useful for enabling the practitioner to allocate an initial distribution of TAIR values within a space to create a planned distribution of visual emphasis, and then subsequently to adjust those values to generate the chosen spatial brightness while maintaining the illumination hierarchy.
Figures 4 and 5 compare two distinctly different lighting distributions in upmarket retail display areas. In Figure 4, large, reflective surfaces are washed with light to create a moderately high level of spatial brightness, and while higher levels of target illuminance are directed on to merchandise displays, the scope to create high levels of TAIR and visual emphasis is limited. In Figure 5, light is focused only on to displays, and surrounding surfaces all have low reflectances. This generates a low level of spatial brightness in which high TAIR values are achievable and strong levels of visual emphasis are created.
The output of the LiDOs procedure is a direct flux distribution (DFD) that informs the practitioner; deliver these flux quantities on to your chosen target surfaces to achieve both your intended spatial brightness level and your envisaged distribution of visual emphasis. This is the form in which the DFD provides the lighting practitioner with the information needed to select appropriate luminaires and to determine their locations, aiming angles and controls.
THE LIGHTING SOLUTION
The LiDOs Procedure starts with the lighting practitioner describing the lighting design objectives for each space within a project. For each space, the outcome of the procedure is a
direct flux distribution specification that enables an informed search for luminaires that can be located and aimed to generate the combination of a chosen level of spatial brightness and an illumination distribution optimised for either efficient flux utilisation or for a planned distribution of visual emphasis.
Even so, in its present form the procedure is not an all-embracing solution as other design aspects may need to be specified as objectives, such as light colour or long-term circadian effects, and these would need to be dealt with as separate issues.
Unless light sources are totally concealed, their presence will add visible components to the lighting design and selection needs to be made with concern for how the luminaires will affect the overall scene. Adding bright elements within a space inevitably has the effect of darkening the appearance of surrounding surfaces and thereby reducing spatial brightness.
While this would be undesirable for situations where avoidance of discomfort glare is a concern, it could be supportive of a lighting design objective to create ‘sparkle’,7 as shown in Figure 5. In this case, a luminaire has been added for its visual effect, and whenever this is done, consideration needs to be given to how other LiDOs may be affected.
Use of the LiDOs Procedure requires the practitioner to select a level of spatial brightness
indicating how brightly lit, or how dimly lit, the space is to appear. The chosen SB level enables an MRSE value to be specified, and the spreadsheet enables the required first reflected flux to be determined. At this point, the practitioner can opt to distribute flux within the space either to generate the MRSE with optimal flux utilance, or alternatively, to achieve an envisaged distribution of visual emphasis. At its most basic, the procedure ensures a space that is adequately and efficiently lit, and if pursued through to its ultimate, it may lead to the development a complex and tightly controlled distribution of flux to provide for precisely defined lighting design objectives.
The author acknowledges with sincere thanks the comments contributed by Dr Peter Boyce to several drafts of this article.
Referrals have been made to the LiDOs Procedure throughout this article, and readers can follow the link below for more information including a worked example, a downloadable LiDOs Spreadsheet and a bibliography on the procedure that includes source details of the documents referred to in the text: tinyurl.com/bdhyspkx
� Table 3: typical visual emphasis assessments for target/ambient illuminance ratio (TAIR) values
� Fig 5: display lighting focused on to target surfaces with low-reflectance surrounding surfaces enables high levels of target/ambient illuminance ratio in this jewellery store. Note that the display lighting sources are concealed, and that the prominently visible pendant is not actually there to provide illumination – it is to provide sparkle
The dynamic and evolving landscape of the lighting industry has brought both opportunities and challenges, particularly in the context of energy efficiency and sustainability. The government’s Energy Technology List (ETL) plays a crucial role in shaping and improving general industry standards. It is extremely relevant to the lighting sector in ensuring that products meet stringent energy-saving criteria, as well as signposting and supporting specifiers and purchasers.
When discussing and examining the different areas of the lighting industry, the office sector in particular emerges as a primary target for adopting new lighting technologies aimed at reducing carbon emissions.
'Focusing on lighting can make a notable difference in energy consumption, often accounting for 30 to 32 per cent of total energy use in office buildings,' says Sophie Parry, chair of the SLL's technical publications committee. Conversely, in other sectors such as data centres, lighting energy constitutes only one to 1.5 per cent of the total energy demand,
rendering its impact comparatively negligible.
Post-Covid, the office sector is witnessing a gradual resumption of normality, with employees being encouraged to return to office spaces. This shift is driving landlords to upgrade building technology to meet minimum EPC ratings, often necessitating the replacement of outdated fluorescent lighting with advanced LED technologies. 'LED technologies have advanced, making it unsustainable to continue with older lamp technologies such as fluorescent and discharge lighting,' says Parry. 'These are being phased out of manufacture, starting last year through to 2027, by the Restriction of Hazardous Substances Regulations.'
Despite its environmental impact, many buildings, including major and international transport hubs, still rely on fluorescent lighting. The ETL plays a crucial role in this transition by providing a framework for selecting energyefficient lighting solutions.
As one of the world’s largest and most comprehensive databases of energy-saving technology, covering 21 technology families and
65 individual sub-technologies, the ETL helps shape industry standards. It supports UK businesses and the public sector by offering advice, support and information on energyefficient products.
The database includes around 8000 rigorously tested and assessed products, ranging from heating and cooling systems to refrigeration and professional foodservice (catering) equipment. Products listed represent the top 25 per cent most energy-efficient in their class and are associated with industry best practices.
THE ETL AND LIGHTING
The ETL’s lighting category includes not only lighting products but also building lighting controls, offering numerous benefits for manufacturers and their clients, including specifiers and facility managers. The ETL lighting criteria have transitioned from an 'unlisted' series of sub-technologies to being eligible for independent listing on the site. We are now actively looking to work with manufacturers and suppliers to submit their first series of applications.
The ETL's government backing and impartiality provide assurance and credibility, making it easier for clients to find, compare and source products that meet stringent energy efficiency criteria. Increasingly being aligned with Government Buying Standards (GBS) and policy decisions, the ETL supports the increasing demand for energy-efficient products and also helps to simplify the application process for manufacturers.
BALANCING DESIGN AND BUDGET
The SLL audience, many of whom are deeply involved in energy efficiency discussions, often face a dichotomy between creating highly efficient designs using the latest technology and pressure from clients to reduce costs.
Lighting designers and engineers strive to create efficient, compliant designs that exceed Part L of the Building Regulations, setting high standards for energy efficiency. However, 'clients often demand cheaper alternatives or less efficient products, reducing future-proofing efforts,' says Parry.
Clients frequently perceive lighting upgrades
� Lighting often accounts for 30 to 32 per cent of total energy use in office buildings making the sector a primary target for lighting technologies that reduce carbon emissions
as a necessary but begrudged expense, focusing on the return on investment (ROI). ROI calculations for lighting upgrades can vary significantly based on the technology being replaced and usage patterns.
The ETL offers a crucial framework to navigate this challenge. By listing products that meet stringent energy-efficiency criteria, the ETL provides assurance and credibility. This endorsement helps lighting designers meet employer requirements and justify the use of higher-quality, energy-efficient products to clients concerned with budget constraints.
For manufacturers concerned about the additional cost and effort of testing their products to meet ETL standards, a significant amount of effort has gone into aligning the ETL criteria with existing measurement and test standards specified by product regulation. As a result, the criteria specify existing test methods and commonly used performance parameters required by the market.
No additional or new testing should be required for the ETL – it’s rather a case of repurposing existing test reports that demonstrate conformity with regulations. This therefore reduces time and resources for the applicant and removes barriers to application.
Furthermore, the ETL criteria permit multiple different ways to demonstrate the conformity of products with the performance requirements. For categories covering Efficient White Lighting Units and White LED Lighting Modules for Backlit Illuminated Signs, for example, this includes 'representative testing', where a product family approach is applied to the procedure. For Building Lighting Controls, performance testing is not required – rather, product functionality is demonstrated through the submission of technical specifications and instruction manuals by the applicant. Further information can be found within the individual sets of criteria.
REDISCOVERING THE BENEFITS OF THE ETL
Since the removal of Enhanced Capital Allowances, the clarity around the revised benefits of registering products with the ETL is not widely known, and many in the industry are unsure of how to leverage it today to promote their energy-efficient products and to further the UK’s goal of a net zero future.
'A few years ago, the ETL was wellunderstood and actively promoted to clients and customers. Now, however, many are unsure
of how it works and where the benefits lie,' says Parry. This uncertainty undermines the ETL's potential to drive investments in sustainable lighting solutions.
While the focus on energy efficiency remains strong, the industry's perception of the ETL needs updating to reflect current realities. The ETL can play a crucial role in recognising and supporting new technologies and research findings, contributing to the industry's progress towards net-zero carbon emissions.
Listing on the ETL provides numerous advantages for both manufacturers and their clients. It offers an additional sales channel, free marketing and promotion, monthly newsletters, LinkedIn and YouTube videos, enhancing product visibility and connecting buyers with sellers. Its rigorous compliance assessment ensures that products meet high standards, providing confidence to buyers and reducing the risk of greenwashing.
The ETL’s platform promotes manufacturer details, documents and contact information, facilitating easier connections between buyers and sellers.
Moreover, it encourages innovation through New Technology Proposals (NTPs), inviting manufacturers to propose new technologies based on their energy-efficiency and sustainability merits. This approach ensures that the ETL remains at the forefront of industry advancements, aligning with both GBS and policy decisions.
NTPs allow manufacturers and suppliers to influence the future direction of the ETL, ensuring the scheme reflects both market demand and also innovation in technology. By creating criteria – and thus verification for innovative products – it will also be helpful in overcoming barriers that new products on the market can sometimes face, when struggling to prove their performance and cut through to specifiers and purchasers.
Lighting ranks within the top 10 most-viewed pages on the ETL site. More importantly, among product-specific pages (families and subtechnologies) and over the past 12 months, lighting ranks third in product-specific page views, following heat pumps and refrigeration equipment. Between April-June 2024, lighting surged to the top position, followed by PFSE (professional food service equipment) and refrigeration equipment for product-specific searches. This trend only underscores the growing interest and demand for lighting products on the ETL.
RECOGNITION FROM THE ENERGY SECTOR
The value of the ETL is widely recognised across the energy sector, and feedback from various organisations and manufacturers highlights its credibility and benefits.
Andy Threlfall, technical and policy director at the Foodservice Equipment Association (FEA) commented that, 'listing products on the ETL confirms compliance, that they meet certain criteria for efficiency, energy performance and the standards created for the ETL scheme –essentially a bit more rigorous than the level to which people tend to test their products.
'So being on the ETL is a way of promoting that your products meet the strictest efficiency targets and specific requirements for the UK market,' continues Thelfall. 'It provides stability for end users because everybody selling you an item will tell you theirs is the best, but [the ETL] is somewhere that the operator can go to compare equivalent machines.'
Sam Carson, technical advisor at heating and hot water appliance manufacturer Rinnai UK, offers another endorsement: 'The reason we have products listed on the ETL is because it definitely gives people some confidence in the products and the manufacturer – it shows that you are very happy to go through the verification procedures of independent bodies. The ETL team were great to work with. It was a very smooth, efficient process. There are no downsides to it, really.'
With thanks to Sophie Parry, chair of the SLL's technical publications committee, and head of Trilux UK Akademie and Lighting Solutions Design, for her input and technical advice
Tom Lock is programme director for the government’s Energy Technology List (ETL) and also consulting director at strategic consultant ICF
To apply, go to: etl.energysecurity.gov.uk
For further details contact the ETL at: info@etl.energysecurity.gov.uk
More information is also available at the ETL's How-To videos on its YouTube channel, outlining how to streamline product search and list products, and providing an easy guide through the process for both manufacturers and specifiers
COLOURFUL LANGUAGE
Frankie Boyle describes herself as a creative director and artist specialising in immersive and experiential design. She has worked in television (Strictly Come Dancing, Tipping Point, among many shows), devised spectacular lighting elements for events such
as the Brit Awards and Glastonbury, and created immersive art installations and experiences that guide audiences through transformative journeys. 'My mission in life,' she says, 'is to allow people to connect with themselves.'
and rigorous, taking her from TV studio to electronics lab, and from entertainment to, ultimately, a more expressive, immersive artistic sphere. Throughout her language has been light and colour. A trite phrase in some ways, but in her case particularly meaningful and fundamental.
'My mission in life is to allow people to connect with themselves'
� Living Lantern is a public artwork changed by the wind, and a series of slow, abstract light animations. By night, light is emitted from the lantern's core. The petals open and close creating beams of colours of varying intensity. 'The effect is hypnotising and dreamy… the lantern encourages the audience to reach a meditative state through its perceived controlled breath'
Boyle was diagnosed with developmental learning disorder (DLD) and dyslexia at the age of seven. As she explained in an interview last year with arc magazine, growing up she struggled to communicate with conventional language, but she always understood the language of light.
Over a period of two years, she took part in a medical research project that involved tests to measure what she reacted to and determine how her brain worked. This often involved putting her into a sensory room with fibre optic lights. 'My parents could see that I always wanted to be in the fibre optic room, I always wanted to do things with light,' she told arc.
'I realised that I had a very heightened sensitivity and receptivity to light and how it was interacting within that space. I subconsciously had this feeling of knowing how lighting could make people feel comforted or seen, or allowed them to move through spaces easier, and I didn’t really know why until I went to university and started to understand more about the psychology and science behind it.'
She studied three-dimensional design at the University of Brighton, and while this entailed a variety of materials – wood, metal, plastics and ceramics – light continued to figure strongly.
'It wasn’t until my art foundation that my tutor turned to me and said, "you do realise that in everything that you do, you’re involving light?" I had even woven fairy lights through my sketchbook, but I was completely oblivious to this,' she says. 'I suddenly became very aware of it, and wanted to harness it, so for my final year project, I knew I wanted to help people with
dyslexia and memory disorders, like me.'
The project involved creating coding for a light source that would 'trigger the nervous system into a memory cortex'. 'Hearing sounds or alarms suddenly makes us go into fight or flight, whereas seeing a colour variation sticks within our primitive scale of understanding, our biological hardwiring of why we have colour in nature,' she says. “That’s how I started, and how I started learning about DMX and about how to control lighting through computers. As soon as I started to understand that whole world, it opened my eyes to a lot of exciting things.'
Boyle knew that she wanted to work in lighting, but wasn't clear which aspect to focus on. Then watching Strictly Come Dancing, she was struck by the lighting. She tracked down the contact details of the lighting director, Mark Kenyon, and the upshot was a six-month apprenticeship with him, working on a range of light entertainment TV shows.
Alongside her work in television, she was looking to develop a portable light tile that she had been working on since before university. Her parents are chefs, and having helped them as a server, she was inspired to develop an illuminated tray to serve canapes for night-time garden parties. Teaching herself the rudiments of electronics and how to solder a circuit, she had developed the tile. 'Not only did it help people to see the food, but it allowed the servers to walk through the crowd, and the crowd parted around them, so I knew there was something in it.'
After six years in TV, she developed the idea, teaming up with the lighting company involved with Tipping Point to produce what became the Lumi Board. She worked with them for three years, eventually becoming its key creative person and devising 'some amazing bespoke items for Ellie Goulding, the Brit Awards and Glastonbury Festival'. (Glastonbury involved three massive LED pixel-mapped jellyfish costumes worn by aerial performers for the Arcadia Spectacular.)
In spite of the charisma and cachéof
� An immersive experience for Magnum ice cream for the launch of their new products for 2024/25: bespoke technology provided each customer with a unique biometric reading, determining their personalised journey. 'Collaborating with sound designer Andrew Beaton, we crafted a unique and hypnotic narrative to enhance the experience'
� Frankie Boyle with Convergence at music charity Bristol Beacon. The sculpture, a collaboration with the Future Proof mentoring scheme for local 18-25 year old musicians, involved choreographing the lights to eight pieces of music they created. It 'encapsulates the sound, light and emotion that converges and runs through the Bristol Beacon, from the cellars to the concert halls above'
television, Boyle felt that something was lacking when it came to her vision of what light and colour could achieve, and that TV remained a somewhat two-dimensional medium.
'I realised that it was all done for entertainment purposes through a TV lens, but people couldn’t fully experience it in an immersive space,' she explained in her interview with arc. '...There’s this beautiful, amazing lighting that could be harnessed and used in different ways ratherthan being on a set that people will never really experience.'
This realisation was the catalyst for her move into light art, to 'create things that allow people to have awareness of themselves, and of the space around them'.
She has subsequently produced a series of public artworks, including Living Lantern (which has travelled to Hsinchu, Brisbane, Athens and New York) and Biophilia (recently featured at Canary Wharf), as well as collaborating with major brands – among them Tiffany, Samsung and Burberry – creating installations and experiences for launches and events.
Combining scientific inquiry with creative expression, Boyle's work is distinguished by her mastery of colour theory and the psychology of perception. Her installations explore the intricate interplay of light and emotion, creating immersive environments that prompt introspection and self-discovery.
Her heightened sensitivity to light and understanding of human behaviour is reflected in her latest installation, for Light 24. Titled Intra-spectrum, it takes inspiration from her recent explorations of the conscious and subconscious, and uses a harmony of reflection and refraction.
'I want people to immerse themselves within the light that we shine and the light that we hold within through an array of beautiful invigorating colours,' she says, 'This installation is all about eliciting introspection and connection.'
Boyle particularly wanted to focus on our relationship with colour. Colour theory is a fundamental concept in art, design and psychology that helps explain how colours interact, how they can be harmonised, and how they affect human perception and emotions.
She believes that as children we are attracted to colour as our eyes are more sensitive and stimulated by brighter colours, yet as we grow older we start to eliminate colour from our lives because we associate it with immaturity and youth. Her work therefore aims to 'reignite those rich emotional experiences that influenced how we felt, thought and behaved through play when we were younger'.
To create the kaleidoscope of colours in the artwork, Boyle uses dichroic film, exploiting the colour-shifting effect which occurs when the material is viewed from different angles.
This happens because the film selectively reflects and transmits certain wavelengths of light while others pass through, creating a multi-colour appearance depending on the observer's position.
The work is very much a summation of her journey so far as an artist, exploring light’s dynamic effects on mental health and human behaviour, 'advocating for its therapeutic potential in immersive art'.
'Light and human behaviour were definitely the first languages I understood,' she says. 'That is why I am so interested in the human response to my work, physically, psychologically and emotionally. Ultimately, light is a language that everyone speaks that taps into the subconscious, connecting us to a space.'
Visitors to LiGHT 24 will be able to view Frankie Boyle's exclusively created art installation, Intra-spectrum, powered by Formalighting, in the space between the main exhibition and the seminars.
Some details and quotes are sourced from an interview featured in arc magazine in 2023. To read the full interview go to: www.arc-magazine.com/frankie-boyle/
For more details of Frankie Boyle's work go to: www.frankieboylestudio.com/
LiGHT 24, supported by the SLL, takes place at the Business Design Centre in Islington, London, on 2021 November 2024.
For more details and to register free: www.lightexpo.london/
The talks programme on the Gallery Level on each day is split into themes, with Wednesday covering the business of design, interiors and lighting, while Thursday focuses on wellness, sustainability and designing for the environment. The Associations Lounge on the same level will feature talks run by the SLL and other bodies.
For the full talks programme go to: www.lightexpo.london/talksprogramme/
� Field of Hearts, for the launch of the Samsung Galaxy S10: set within a 5m x 5m mirrored cube, the installation depicted a tactile wheat field crafted from custom fibre optics and mirrors. The light movements and colours were influenced by participants' heart rates, resulting in 'a unique light symphony for each couple'
AT FACE VALUE
Alan Tulla finds papers on lighting for pedestrian reassurance – and correspondence featuring a comparison between black and white cats
If you have ever been unsure about the actual meaning intended by an emoticon or emoji there is an interesting paper by Y Mao and S Fotios. A lot of lighting research about how safe pedestrians feel after dark is based on looking at images of faces under varying lighting conditions. One of the main factors being, of course, the vertical illuminance on the person’s face.
In almost all cases, the image presented to the viewer is full face – just like a passport photo. Pedestrians want to know if the person coming towards them is friend or foe. This is known as a facial emotion recognition task (FER).
The paper 'Road lighting for pedestrians: Comparing full-face with three-quarter views in a facial emotion recognition task' does just that. The approach taken used a mathematical model called relative visual performance (RVP), which accounts for size and contrast of the task (the face), the age of the observer and the adaption luminance. Other variables included both dark and pale skin, The main conclusion is that the three-quarter
view leads to lower recognition than full face. This is independent of the luminance.
The paper by L Wei, G Bizjak and MB Kobav, 'Evaluating the impact of road lighting on pedestrian reassurance through the day-dark approach', describes a field study in Ljubljiana, Slovenia, using the day-dark methodology.
If, like me, you are not directly involved in lighting research, you may not have come across the concept of the day-dark approach. The intention is to minimise the effect of any non-lighting factors and the complexity of fully grasping the varied requirements of the average pedestrian. This fivepoint scale was proposed by Boyce et al in 2000 and later implemented by Fotios et al.
By assessing the same location under both conditions, the day-dark method reduces the influence of environmental discrepancies, thereby offering a more accurate depiction of the actual contribution of the road lighting.
Optimal lighting conditions are those which have the smallest day-dark difference.
The field study was carried out in 12 locations
along a 3.5km path in Ljubljiana. The study aimed to answer two questions: a) What is the optimal horizontal illuminance for pedestrian reassurance? and b) Does minimum illuminance serve as a better predictor of reassurance than does average illuminance or uniformity?
The path passes through lots of different urban areas and the paper includes daytime photographs so that comparisons can be made by the reader with the data collected. This data is then collated and the day-dark difference calculated.
The overall conclusion is that a minimum illuminance of 1.8 lux with good uniformity (typically >40 per cent) provides a day-dark difference of 0.5 units. This is similar to a study in Sheffield which advocated a minimum of two lux.
The implications of the study suggest a shift towards prioritising minimum illuminance and uniformity rather than a combined focus of both mean and minimum illuminance levels.
Finally, one of the pleasures of reading LR&T is the correspondence from other readers. There is a deeply informative but delightful letter from P Boyce, C Cuttle, A Durante, K Kelly and P Raynham discussing 'spatial brightness' (see also Kit Cuttle's article on p5). They make a comparison between a black cat on a sunlit windowsill with a white cat some distance away.
Alan Tulla is a former president of the SLL and principal of the independent consultancy Alan Tulla Lighting
Lighting Research and Technology: OnlineFirst In advance of being published in the print version of Lighting Research and Technology (LR&T), all papers accepted for publishing are available online. SLL members can gain access to these papers via the SLL website (www.sll.org.uk)
Road lighting for pedestrians: Comparing full-face and 3/4 views in a facial emotion recognition task
Y Mao and S Fotios
Evaluating the impact of road lighting on pedestrian reassurance through the daydark approach
L Wei , G Bizjak and MB Kobav
Correspondence: What do we mean by spatial brightness?
Peter Boyce et al
� Photographs of face models in the full-face and three-quarter views used in trials (Road lighting for pedestrians, Y Mao and S Fotios)
ELEMENT OF SURPRISE
Helen Loomes chooses five cases where light adds a new dimension
Ithink I have probably always been aware of light, even before I was involved in the industry, and I still feel the awe, even a physical response, to some effects.
So my top 5 is an eclectic mix of examples, from sculpture to sacred building, where light has brought a new dimension. This could be adding texture with light and shade, or adding an element of joy, that touch of fun. Daylight is the master in this respect, and we are always learning from nature. However, for some artists and designers light is in their first thoughts, right at the beginning of the artistic process.
Helen Loomes is immediate past president of the Society of Light and Lighting
Feria del Caballo, Jerez de La Frontera
The annual festival in the southern Spanish city is an exciting weeklong gathering to parade horses and Spanish traditions. This is not a tourist event but a celebration for the Spanish who all dress in their finest traditional costumes. Music is everywhere, compelling people to dance. The party comes into its own after dark. The huge park, crisscrossed with avenues lined with bars and restaurants, starts to glitter with lights which compounds the sense of excitement.Here the lighting adds magic, majesty and spectacle, transforming the ordinary.
Helaine Blumenfeld sculpture
Helaine Blumenfeld has told me how she envisages the light permeating some sections of the sculpture, creating contrast with denser overlapping sections. This ethereal effect is wonderfully beautiful. I had the privilege of working with her for an exhibition at the Royal British Society of Sculptors. In addition to lighting the pieces we painted the walls black. The results really showed off the extraordinary shapes, adding depth to the already beautiful marble.
Catedral-Basílica de Santa María, Palma, Mallorca
Colourscape, Waddesdon Manor
At the other end of the scale is an immersive light experience held at Waddesdon Manor, near Aylesbury, Buckinghamshire (and other venues). Colourscape is a series of tented tunnels lit with primary colours. Each person was given a differently coloured cape and encouraged to run through the tunnels. It was an elemental lesson in showing how colours respond to different wavelengths of light, but my granddaughters just loved being immersed in a primaeval reaction to light.
World Trade Center Hub, New York
Clever architectural contrivance – here by Calatrava – brings the cathedral phenomenon into the future. The wings of the hub's structure culminate in the Oculus, allowing daylight to flood in, filtering down through to all levels.The structure also ingeniously uses light to create a moving memorial to 9/11. Its opening roof is precisely calculated so that when it retracts each 11 September, at 10.28am to mark the time of the 2001 tragedy, the orientation of the sun delivers a strip of light down below. The light, and the void, deliver the message. 1 4 5 3 2
Religions the world over understand how light adds to the spiritual experience. Walking inside Palma's cathedral, I was amazed by the light through the rose window. The colours merged across the space tinting everything in their path including people, generating a hush, a sense of awe. The 'spectacle of eight' occurs only on 2 February and 11 November (saints' days). Complex calculations mean that when the light passes through the main rose window, its reflection is projected on to the wall in front, forming a double rose window.
Events 2024
For details of all upcoming webinars, go to: www.cibse.org/societyof-light-and-lighting-sll/sll-events/upcoming-webinars-and-onlinecontent
For previously recorded CPD webinars (including regional webinars), go to: https://www.cibse.org/get-involved/societies/society-of-lightand-lighting-sll/sll-events/on-demand-webinars-past-presentations
EVENTS
SUSTAINABLE SMART LIGHTING WORLD CONFERENCE
Date: 12-14 November
Venue: Eindhoven University of Technology www.ssleindhoven.com/home
LIGHT2PERFORM 24
(Organised by the SLL as part of CIBSE's Build2Perform and including the official announcement of the SLL Young Lighter 24 winner)
Date: 13-14 November
Venue: ExCeL, London www.build2perform.co.uk/light2perform
LIGHT 24
Date: 20-21 November
Venue: Business Design Centre, London N1 www.lightexpo.london
2025
LIGHT+INTELLIGENT BUILDING MIDDLE EAST
Date: 14-16 January
Venue: Dubai World Trade Center https://light-middle-east.ae.messefrankfurt.com
WORKSPACE DESIGN SHOW
Date: 26-27 February
Venue: Business Design Centre, London N1 https://workspaceshow.co.uk/
EUROLUCE
Date: 8-13 April
Venue: Milan Fairgrounds www.salonemilano.it/en/exhibitions/euroluce
CIE MID-TERM CONFERENCE
Date: 7-9 July
Location: Vienna https://vienna2025.cie.co.at/
LET DIPLOMA IN LIGHTING DESIGN
For details and registration: www.lightingeducationtrust.org
