Light Lines November/ December 21

The Society of Light and Lighting

LIGHT LINES

VOLUME 14 ISSUE 6 NOVEMBER/DECEMBER 2021

THE RIGHT WAVELENGTH Cleaning up with UV

GOOD OFFICES The new workplace standard

Editorial

November/December 2021

FROM THE EDITOR SECRETARY Brendan Keely FSLL bkeely@cibse.org SLL COMMUNICATIONS MANAGER Juliet Rennie Tel: 020 8772 3685 jrennie@cibse.org EDITOR Jill Entwistle jillentwistle@yahoo.com COMMUNICATIONS COMMITTEE: Linda Salamoun MSLL (chair) James Buck Iain Carlile FSLL Jill Entwistle Chris Fordham MSLL Rebecca Hodge Eliot Horsman MSLL Stewart Langdown FSLL Luke Locke-Wheaton Rory Marples MSLL 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 2022 IS 8 NOVEMBER PUBLISHED BY The Society of Light and Lighting 222 Balham High Road London SW12 9BS www.sll.org.uk ISSN 2632-2838 © 2021 THE SOCIETY OF LIGHT AND LIGHTING The Society of Light and Lighting is part of the Chartered Institution of Building Services Engineers, 222 Balham High Road, London SW12 9BS. Charity registration no 278104

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The arrest of Recolite CEO Nigel Harvey, for the third time, at a London Extinction Rebellion protest (News, p4) should give us all pause for thought. There will be deeply divided opinion over the controversial disruptive actions of XR, just as there was over the Suffragette movement and Gandhi's passive resistance campaign. But, rightly or wrongly, such actions are generally born out of frustration when nothing else seems to work.

We have known about our deleterious effect on the planet for decades, possibly centuries. A pronounced global warming trend was noted in the 1930s, for instance, and there is more than a little irony in the following statement from Thomas Edison, co-developer with Joseph Swann of the light bulb: 'We are like tenant farmers chopping down the fence around our house for fuel when we should be using Nature's inexhaustible sources of energy – sun, wind and tide... I'd put my

money on the sun and solar energy. What a source of power! I hope we don't have to wait until oil and coal run out before we tackle that.'

Vested interests – personal, corporate, political and national – are a clear and complex barrier to achieving the ultimate act of selfinterest: saving our planet. It is not that we are not doing anything but that we are not doing enough and we are not doing it fast enough.

Things change at glacial speed. Sadly that metaphor is increasingly inappropriate as our glaciers melt at an alarming rate.

JILL ENTWISTLE JILLENTWISTLE @YAHOO.COM

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 (2006) SLL Lighting Guide 5: Lighting for Education (2011) SLL Lighting Guide 6: The Exterior Environment (2016) SLL Lighting Guide 7: Office Lighting (2015) SLL Lighting Guide 8: Lighting for Museums and Galleries (2021) SLL Lighting Guide 9: Lighting for Communal Residential Buildings (2013) 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 Design Guide (2015) SLL Lighting Guide 13: Places of Worship (2018) SLL Lighting Guide 14: Control of Electric Lighting (2016) 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) Guide to Limiting Obtrusive Light (2012) Code for Lighting (2012) Commissioning Code L (2018) SLL Lighting Handbook (2018) CIBSE TM66: Creating a Circular Economy in the Lighting Industry (2021)

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Secretary’s column/Contents

November/December 2021

They are like buses. You sit patiently waiting for a new publication from the Society of Light and Lighting and then you get three turning up, one after another. But we are pleased to say that the following new publications are available to download or purchase from the SLL website: LG8: Lighting for Museums and Art Galleries. The previous edition of this guide was published in 2015. The new publication, authored by Mark Sutton Vane (Sutton Vane Associates), brings you up to date with all the factors to be considered when lighting artefacts and spaces with both conservation and the visitor experience in mind. Obviously, there is a great deal of change from the 2015 publication regarding light sources.

LG21: Protecting the Night-time Environment. This brand-new guide was authored by SLL past president Liz Peck, who sadly died in January. Liz had taken the draft of the guide close to completion and it was deemed appropriate to keep as much of her work as she left it. Benedict Cadbury kindly agreed to make the final minor amendments to the publication.

CIBSE TM66: Creating a Circular Economy in the Lighting Industry. The Technical Memorandum (TM) sets out what is entailed in designing and manufacturing to comply with CE principles. It includes a check list, a method of assessing a product's performance in terms of the circular economy, and real-world examples of good practice. The TM project lead was SLL immediate past president Bob Bohannon, while Kristina Allison, chair of the SLL education committee, project-managed the draft.

A big thank you to Simon Robinson and Sophie Parry, previous and current chair respectively of the SLL technical and publications committee, as well as the authors and contributors to the guides who have worked very hard to ensure their production.

In the last edition of Light Lines I said that in September Eleftheria Deko would do a webinar presentation of her lighting scheme for the Acropolis. Unfortunately, we were unable to bring this presentation to you at the scheduled time but the webinar will be rescheduled and all details can be found under the events section of the website.

We are pleased to confirm that the final of the SLL Young Lighter 2021 will take place online on 16 December. The four finalists, again all female, and their papers are as follows:

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• To download SLL Lighting

Guides: www.cibse.org/society-oflight-and-lighting-sll/sllpublications-and-guidance • To register for the SLL Young Lighter online final: www.cibse.org/society-oflight-and-lighting-sll/sllevents/sll-young-lighter

• • • •

Remedios María López Lovillo: Adaptive lighting control system – user-oriented Kate Turley: Biodynamic Lighting to Support Wellbeing in Dementia Maria Englezou: Do we need to change the design of healthcare facilities rooms?

María Teresa Aguilar Carrasco: Lighting Optimisation in 24-hour work centres to promote a good circadian rhythm

We hope you will all attend and support the SLL Young Lighter finalists (see box for registration details). The winner of the competition will receive a year's free SLL membership, £1000 and, of course, the SLL Young Lighter trophy.

A big thank you to the CIBSE North West regional committee for letting me join the regional members at the September BBQ. A CPD presentation by Zumtobel was followed by the social and networking event, a very enjoyable evening.

It was also great to see so many SLL members and friends at the [d]arc room pop-up @Design London and [d]arc night, also in September. A very good event with fun and interesting people, presentations and exhibitors.

You should all have received your renewal notification for your 2022 SLL and CIBSE membership subscription. We hope you will continue to support the society and enjoy the benefits of membership. Going forward, many of the SLL webinars will remain free to members with non-members being charged a small fee. If you have any questions regarding the membership benefits or renewal process, please do contact me.

BRENDAN KEELY BKEELY @CIBSE.ORG

Contents 2

EDITORIAL

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SECRETARY'S COLUMN

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NEWS

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WORK IN PROGRESS Sophie Parry analyses the new BS EN standard on lighting the workplace, getting its first update in a decade

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GLOWING VIRAL The pandemic has triggered a new interest in the use of UV light for disinfection. Mike Simpson explains the technology, the terminology and the considerations for its use

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SUN PROTECTION How artist and innovator Daan Roosegaarde has turned UV-C into a social beacon for public spaces

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SEEING AND NOT SEEING Following a recent SLL webinar, Dr Shelley James and Dr Denize Atan examine lighting for both the visual and non-visual systems

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A MEASURED APPROACH Lighting art and the assessment of metrics feature in the latest LR&T papers, discovers Iain Carlile

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EVENTS

COVER: Urban Sun by Studio Roosegaarde, a far-UV-C light installation designed as a virus sanitiser and social beacon

Courtesy of Studio Roosegaarde

FROM THE SECRETARY

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News

November/December 2021

THE LATEST NEWS AND STORIES

RECOLIGHT CHIEF ARRESTED

YOUNG LIGHTER FINALISTS REFLECT DIVERSITY OF LIGHTING ISSUES The four finalists for the 2021 SLL Young Lighter competition reflect the diversity of topics which currently concern the lighting profession, especially aspects of health and wellbeing.

Kate Turley will examine biodynamic lighting that supports wellbeing for those with dementia, while María Teresa Aguilar Carrasco will look at how lighting in 24hour workplaces can be optimised to promote circadian rhythms. Also in the line-up are Remedios María López Lovillo, whose subject is a user-oriented adaptive lighting control system, and Maria Englezou, who asks whether we need to change the design of healthcare facilities rooms.

They will each give a presentation in the online final on 16 December.

ILP APPOINTS NEW HEAD The Institution of Lighting Professionals (ILP) has appointed Justin Blades as its new chief executive officer. He succeeds Tracey White, who is relocating abroad. Joining the ILP on 1 November, Blades previously held senior positions in the membership sector, including six years as deputy chief executive of the Institution of Chemical Engineers, one of the largest chartered professional engineering institutions in the UK.

Continuing our occasional series on lights made out of weird stuff, we have a case of rind over matter with the 3D-printed Ohmie lamp from Milanbased start-up Krill Design.

Each lamp apparently contains the peel of two Sicilian oranges. Waste from the food industry, they are dried, ground into a powder, then mixed with a plant-derived biopolymer. This mix is extruded in the form of a filament and used to build the lamp using fused deposition modelling (FDM).

The luminaire, which is 23cm tall and has an output of 70 to 90lm, actually has

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Nigel Harvey, CEO of lighting and electricals recycling body Recolight, has once more been arrested during climate action protests in London. He was one of a group of Extinction Rebellion (XR) climate activists who took part in an August protest to raise awareness of the climate crisis.

As part of the protest, Harvey (pictured below) was 'locked' for more than 20 hours to a giant pink table erected by XR at a busy junction near Leicester Square tube station.

'The recent IPCC report was crystal clear,' he said in a statement following his release. 'Unless immediate and radical action is taken to decarbonise our societies, we face climate breakdown, with a bleak outlook for humanity. I find that prospect terrifying.'

He acknowledged that XR is disruptive but said he felt that inaction from governments had left him with little alternative. 'While our governments fail to act, it is the only option left that might drive the change we all need.

'Like many people, I’ve tried to do the right thing,' he continued. 'Signing petitions, lobbying MPs, changing my behaviour and encouraging others to do likewise, have all failed. The emissions keep rising.'

Harvey was arrested on 24 August and taken to Walworth police station. He was charged with failing to comply with a police instruction to end the protest, and released on the same day. He was also arrested in October 2019 and September 2020 while taking part in other climate protests.

the texture, colour and delicate smell of an orange. You can even put it on the compost when you're fed up with it. www.ohmie-krilldesign.net

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Standards

November/December 2021

Oculus Light Studio

2021 IALD Award of Merit-winning Amazon Nitro in Seattle, lighting design by Oculus Light Studio: lighting designers need metrics that befit contemporary offices and their occupants

WORK IN PROGRESS Sophie Parry analyses the new BS EN standard on lighting the workplace and asks whether the people who actually use the space have been sufficiently considered

B

efore we explore the principles and metrics of BS EN 12464-1, we should be aware that this standard is for consideration by lighting practitioners wishing to work to what is currently accepted best practice. The standard is often cited as a

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performance requirement in the Employer's Requirements for a project.

The legal minimum requirements for lighting in respect of preventing accidents due to poor lighting are found in HSG38 Lighting at Work, published by the Health and Safety Executive.

This HSE document is by no means state of the art best practice for general lighting by today’s standards.

The new edition of BS EN 12464-1 does indeed take into account people's needs – to a degree. It has moved on since 2011

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in respect of further addressing the needs of the occupants who actually use the lit space, but just as the construction industry is doing everything possible to reduce energy usage at the altar of net zero carbon, potentially with higher lighting energy requirements.

This last situation is where lighting and electrical engineering get interesting – in essence, how to deliver more with less.

Let's stop and consider the pros and cons here.

If we adopt the mindset of ‘low energy lighting’ we could become transfixed on just the energy side of the equation, at the expense of lighting quality.

Some of you will remember that the lighting industry has been here before. With the advent of LED luminaires, many upgrade projects were designed on the basis of creating energy savings that showed an ROI, or return on investment, sum that was attractive to the budget holder and therefore the key to project funding. However, replacing older technology luminaires with LED fittings on a like-forlike basis, without reviewing the luminaire performance data or any lighting calculations to ensure the resultant lighting quality met at least the requirements of BS EN 12464-1, was often overlooked – with unfortunate consequences for the staff who worked or studied in these spaces.

On the ‘pro’ side of the equation, we could design for a variety of tasks and take the needs of an older workforce into account, even if these features are not required at the onset, but may be required in the future or if the space has multiple users at different times and with different levels of visual acuity.

Now we are balancing the equation by also considering lighting quality, and should design on this basis to make the lighting installation energy efficient – for the given performance requirement, rather than just a low-energy lighting installation possibly delivering substandard lighting quality. So that said, what’s new or revisited in BS EN 12464-1?

SCALE OF ILLUMINANCE Although the scale of illuminance appeared in the previous standard, this version reinforces its use. The key benefit is to promote the best practice of designing lighting in spaces with task area illumination and, where the space dimensions allow, immediate surrounding area illumination and background area illumination.

In order to design in this way, any upward or downward values from the task area

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illumination should follow the scale of illuminance. These step changes can be achieved either by differing lumen output packages being available for the luminaires or by creating notional lighting control zones and setting illumination levels as part of the lighting installation commissioning works.

The benefits of this approach are that, overall, there is a delineation of lighting levels which makes the space more visually interesting, changes the human perception of the illumination and also gives an overall reduction in lighting energy consumed.

This method of commissioning and optimisation may not be so easy on a Cat A office project, but with the correct product specification, could be adjusted and optimised as part of the Cat B fit-out works. It also begs the question as to why the industry persists with Cat A wall-to-wall task lighting levels on speculative projects, of course. However, without ever knowing where the workstations might eventually be sited and therefore creating the potential for overlighting and excessive use of energy.

Major objects such as furniture and machinery: 0.2-0.6 Clear glass (typical value): 0.1

DISCOMFORT GLARE AND UGR Seemingly there is a new metric – RUGL – used in the application tables in Section 7, but on further delving, it seems that according to the list of symbols and abbreviations included at Section 4, RUG means UGR and RUGL is the RUG limit value. For all that, the UGR values as we know them don’t appear to have changed in the application tables.

The standard does emphasise that the tabulated UGR information used in calculations should be provided by the luminaire manufacturers and that the designer’s proposals should include information on the luminaire(s), room dimensions, room surface reflectances and luminaire space/height ratios. The calculation or checking of unified glare ratings is, in my opinion, quite easy to get wrong or, in the hands of the unscrupulous, easy to manipulate to misrepresent a desktop design.

In order to go some way to help remove the

5 - 7.5 - 10 - 15 - 20 - 30 - 50 - 75 - 100 - 150 - 200 - 300 - 500 - 750 - 1000 - 1500 - 2000 - 3000 - 5000 - 7500 - 10,000 Fig 1: scale of illuminance (lux)

CYLINDRICAL ILLUMINANCE In the previous standard, a modelling ratio was mentioned as a desirable lighting design feature in order to allow a speaker's or presenter's face to be seen more clearly as an aid to non-visual communication.

The revised standard now lists required maintained average cylindrical illuminance metrics via the application tables in Section 7 and with associated guidance, including modelling ratios, in sections 5.6.2 and 5.6.3.

REFLECTANCE OF SURFACES Reflectance from ceilings and walls was previously determined by the use of values relative to the horizontal maintained illuminance value. The revised standard now lists the required ceiling and wall reflectances via the application tables in Section 7.

For design outside of the scope of these application tables, the surface reflectance values are still provided. They have hardly changed and are as follows: Ceiling: 0.7-0.9 Walls: 0.5-0.8 Floor: 0.2-0.6 (this was previously 0.2-0.4)

avoidance of doubt, there is additional guidance in the standard in Appendix A.2.1 on how to approach variables such as irregularly shaped spaces, designs requiring the use of more than one standard luminaire, irregular luminaire positions, deviating room reflectance values and which styles of luminaire need not be taken into account when calculating RUGL from the declared observer positions.

10 - 13 - 16 - 19 - 22 - 25 - 28 Fig 2: R UGL unified glare rating scale of limits

REQUIRED AND MODIFIED ILLUMINATION LEVELS (CONTEXT MODIFIERS) So, we have some expanded and rigorous metrics actually stated in the 52 application tables in Section 7, rather than just notes elsewhere in the standard. In addition there are required or default metrics for each application, and context modifiers. This means that, subject to completing an analysis on the types of people, their eyesight condition and the tasks performed, the default metrics might need to be raised or lowered to take into account the people using the space.

Before we go any further, it would be helpful

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Standards

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to have a look at Table 1 and how context modifiers are determined: Visual work is critical Errors are costly to rectify Accuracy, higher productivity or increased concentration is of great importance

EXAMPLE FOR OFFICES A large open-plan office has a number of activities including writing, typing, reading, data processing and filing/ copying. The computer-based tasks are flexible and may be performed in a number of workstation positions, while the filing/copying is fixed in a number of positions throughout the space.

The staff ages in the space range from mid-20s to early 60s, with the median range in their early 50s. No current members of staff are visually impaired. The office lighting is to be designed in a way to preserve the flexibility of the space while ensuring all the tasks can be performed effectively. The requirements from the schedule at Table 33 for the tasks listed are:

Task details are of unusually small size or low contrast The task is undertaken for an unusually long time The task or activity area has a low daylight provision The visual capacity of the worker is below normal Table 1: context modifiers for increase of maintained illuminance

Raise the stated maintained illumination levels (Em) in the Section 7 application tables and in accordance with the scale of illuminance if: • •

1-2 conditions apply from Table 1 by one step 2+ conditions apply from Table 1 by two steps

Sometimes step changes could be lower than the default maintained illuminance values found in the application tables in Chapter 7:

Table C1: basic requirements from Table 33

Due to the flexible nature of the office, the most onerous requirements must be met throughout the space, which means the requirements for the office are:

Table C2: basic requirements for the entire office

As there is a high percentage of older staff within the space, the required illuminance of 500 lux would be inappropriate. Using the scale of illuminance found in section 5.3.2, the design team proposes that the maintained illuminance should be raised by at least one step, according to the context modifiers:

200 Task details are of an unusually large size or high contrast

-

300

-

500

750

-

1000

-

1500

-

2000

Therefore, the modified requirements become:

The task is undertaken for an unusually short time Table 2: context modifiers for the decrease of required maintained illuminance

Lower the stated maintained illumination levels (Em) in the Section 7 application tables and in accordance with the scale of illumination if: •

Table C3: modified basic requirements for the entire office

As the task illuminance has been raised by one step, the cylindrical, wall and ceiling illuminances should also be raised by one step on the scale of illuminance, thus modifying the overall requirements to:

1-2 conditions apply from Table 1 by one step

On the right is a worked example for offices (reproduced from BS EN 12424-1 2021) where context modifiers are determined and applied, using the expanded application tables in Section 7.

KEY TO TABLES (RIGHT) Cylindrical illuminance: Wall illuminance: Ceiling illuminance:

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Table C4: final basic requirements for the entire office

The 750 lux is only applied to workstations. Any higher lighting energy required can be mitigated with lighting controls, together with the thoughtful choice and positioning of luminaires.

For certain mixed-use spaces such as schools operating during the day and the evenings for adult education, two sets of context modifiers could be applied for day and night with scene selection for both situations made via the lighting control system, as a means of reducing the lighting energy requirements.

In conclusion, the resultant task illumination of 750 lux should be applied where required and not over the entire space, as this could make compliance challenging or even impossible in terms of BS EN 12464-1:2021. Also, blanket lighting to 750 lux could result in unnecessarily large amounts of lighting energy being consumed.

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TEMPORAL LIGHTING ARTEFACTS (TLAS) Information on the limitations of TLAs, specifically flicker and stroboscopic effects are found in Section 5.8 and are based on the IEC metrics short-term light modulation/flicker indicator (PstLM) and SVM (stroboscopic visibility measure). There is also more detailed information for specifiers available in the SLL's Fact File 17 Temporal Lighting Artefacts (available as a free download on the SLL website).

LIGHTING ENERGY NUMERICAL INDICATOR (LENI) Leni and BS EN 15193-1 are cited in Section 6.4. This is relevant as Leni is as good as it gets when checking proposed lighting designs for energy compliance, but is seldom used, as most lighters tend to look at the W/sqm output on lighting plots. This information is useful for determining power densities for lighting circuit design, but is actually the worst-case scenario and not always an accurate representation of the likely energy consumption of the lighting installation over time.

Lighting energy calculation at the design stage needs to improve both in accuracy and granularity given that there is a growing expectation to design for or to support net zero carbon outcomes as far as is possible.

As a method for calculating lighting energy based on the hours of use, illumination levels, daylight contribution, the effects of standing loads and the reduction in energy use

provided by appropriate automatic lighting controls, Leni has been in existence for many years. The output of the calculation is expressed as kWh/sqm/per annum.

The full version can be found in BS EN 15193-1:2017 and A1 2021 Energy Performance of Buildings: Energy Requirements for Lighting. A simplified version can be found in Part L, chapter 12 of the Building Regulations for England.

The Guide to Specification: Best Practice for Offices, published by the BCO (British Council for Offices) also cites minimummaximum Leni values for office applications.

There is also a simplified version of Leni with a worked example in the SLL's LG 14 Control of Electric Light.

Given the above, it could be said that the general trend in more accurate methods of predicting operational lighting energy is, and should move more towards, the Leni method, something which BS EN 12464-1: 2021 recommends.

LED lighting and arguably a better lighting technology (other than daylight) to deliver the non-visual benefits of lighting, we are still trying to make our designs comply with metrics developed in the last century when general purpose electric light was, well, just that.

Of interest in Annex B are the concepts of: • • •

NON-VISUAL AND VISUAL EFFECTS OF LIGHTING You may recall at the start of this article, I made a mischievous reference to people's needs in respect of lighting. Although there are no metrics in the standard, interestingly in Annex B there is a section that looks in part towards what future lighting metrics might look like.

Many in the lighting community agree that electric lighting metrics need overhauling.

Although we have moved into the era of

Toranomon Hills Business Tower, Tokyo, by Sirius Lighting Office, winner of the 2021 IALD Radiance Award for Excellence: 'the benefits of a scale of illuminance are that, overall, there is a delineation of lighting levels which makes the space more visually interesting'

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Mean ambient illuminance (Eamb) – Govén et al1 Mean room surface exitance (MRSE) – Cuttle2 Visual lightness and interest: 40-degree band luminance – Loe et al3

These are examples of some interesting theories and if some applied research is carried out, with beneficial outcomes, the lighting industry may well have some new metrics that are fit for purpose in the 21st century. Standards such as BS EN 12464-1 are updated on average every 10 years and tend to advance cautiously, based on what is proven. Now is the time to do that applied research and build the compelling arguments for change, or this standard might never evolve at a rate required to support the needs of today’s lighting designers.

Sophie Parry, MIET FSLL, is technical applications and lighting education consultant at Zumtobel Group Lighting and chair of the SLL's technical and publications committee The new BS EN 12464-1:2021 Light and Lighting of Work Places. Part 1. Indoor Workplaces is published this autumn and is available from https://shop.bsigroup.com

Fumito Suzuki

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References 1 Govén, T, Laike, T. Ambient lighting as a measure to improve wellbeing and performance. Proceedings CIE 28th Session, Manchester UK, pp 80-86 2 Cuttle, C. A new direction for general lighting practice. LR&T 2013; 45: 22-39 3 Loe, DL, Mansfield, KP and Rowlands, E. A step in quantifying the appearance of a lit scene. LR&T 2000; 32: 213-222

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UV lighting

November/December 2021

GLOWING VIRAL The pandemic has triggered a new interest in the use of UV light for disinfection. Mike Simpson explains the technology, the terminology and the considerations for its use he use of ultraviolet radiation for disinfection is not new. The germicidal effects of ultraviolet light were first discovered in 1877 and the 1903 Nobel Prize for Medicine was awarded to Niels Finsen for his use of UV against tuberculosis of the skin. Using UV light for disinfection of drinking water dates to 1910 in Marseilles, and between 1937 and 1941 upper-room UV was used in suburban Philadelphia schools to prevent the spread of measles. But it gained new attention during the pandemic as a way of reducing the effects of the Sars-CoV-2 virus. Ultraviolet Germicidal Irradiation (UVGI) can disable the structural bonds in the DNA of the virus preventing it from reproducing.

Most sources of UV-C (the shortest wavelength of the three types of UV) are gas discharge lamps in various formats.

The most common ones in use look like traditional fluorescent lamps without the phosphor coating and produce radiation at a wavelength of 254nm. Other types produce radiation at 222nm and there are developments in LED technology which will also produce UV-C. The amount of UV-C required to disable the virus is called the dose, measured in joules. This is the product of the irradiation and the period of time it is used. The susceptibility of the virus to the UV-C also has to be taken into account by its k(λ) factor – a measure of how an individual virus reacts to UV-C – which varies from virus to virus, and whether it is on a dry surface or in suspension in droplets (ISO 15714). It is also affected by the wavelength of UV-C used.

For lighting people, think of the irradiation

Ultraviolet lamps in a water disinfection plant

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Shutterstock

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as lux but without the eye sensitivity component. Then multiply by the time to get the dose.

For the irradiation of surfaces it is possible to use standard lighting software but with units recalibrated into W/sqm instead of lux.

Disinfection in air is rather more complex as we have to think in terms of spherical irradiance, also known as fluence rate, and where the dose is instead termed fluence.

To calculate the fluence we need to know how long a virus will be irradiated. This means that we have to predict the air movement within a space. So when designing air disinfection systems we usually just calculate the fluence rate.

Another new term we have to learn is the log reduction. This is simply the percentage reduction in the virus over a given time.

So a log 1 reduction is 90 per cent, log 2 is 99 per cent, log 3 is 99.9 per cent and so on. So with a grasp of the appropriate terms – irradiance, fluence, fluence rate and log reduction – the lighting designer can transition into a UV-C designer.

Since the start of the pandemic, research has been carried out to confirm that the Sars-CoV-2 virus responds to UV-C in the same way as other viruses. Research conducted by the National Emerging Infectious Diseases Laboratories (NEIDL) at Boston University1 demonstrated that a UV-C dose of 290 J/sqm could achieve a log 4 reduction of the Sars-CoV-2 virus on surfaces. Other research2 has also shown a room with a fluence rate of 40 mW/sqm gave a log 4 reduction in airborne viruses in 10 minutes.

So how is this technology deployed in practice? For surface disinfection we can install UV-C in battens over the area to be disinfected. Disinfection chambers can be used for small items such as keys and phones. But remember that only the surfaces in direct sight of the UV-C source will be treated so anywhere where there are shadows will be missed. So fewer, smaller sources will create less shadow than a single larger one. We are also looking for the minimum irradiance over the surface, not the average, as this will be the worst case in terms of disinfection. Once this has been calculated we can work out the duration of the exposure to give the dose.

Transmission through the air is now widely accepted as the principal way Sars-CoV-2 is

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Action of UV-C on DNA

Upper air UVGI: the small amount of visible blue light in the beam shows where the UV-C is

Surface disinfection from UV-C battens in an automated distribution centre

spread3 and there are various ways that air can be treated by UV-C. This is described in more detail in the CIBSE Covid19 ventilation guide v5 but it falls into the following general techniques:

is harmful to the skin and eyes, and so maximum doses have to be respected.

ISO 15858 allows a maximum dose of 60 J/sqm per day. Most systems for surface disinfection would exceed this limit so the design should take account of the time required to achieve the correct dose and ensure that no access can be made into the room while it is on. In practice this solution is most commonly used in washrooms where surfaces are frequently touched by different people. With the correct dose it is possible to achieve disinfection in a few minutes so a simple interlock with the door will stop entry.

Upper air solutions require the system to be operating while the room is occupied to disinfect the air at source. This means that while a high irradiation is required at ceiling height, it must be limited at head height (1.83m). Therefore these units typically

•

•

•

Upper room UVGI where a narrow beam of UV-C is projected on to the air above head height to deactivate viral material, relying on air mixing in the space In duct UVGI where UV-C lamps are installed in the return or supply air ducts of mechanical ventilation systems to disinfect the air UVGI air cleaners where UV-C lamps are mounted inside an enclosure, with a fan to draw air through

One important factor in the design of a UVGI system is safety. UV-C at 254nm

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UV lighting

November/December 2021

produce a narrow beam in the order of a few degrees.

In these situations, the reflection of the UV-C from the ceiling must be taken into account as it can make a significant contribution to the UV-C at head height.

This is where lighting designers have to change their thinking as surfaces which are highly reflective to light may not reflect UV-C and vice versa. A calcium whitener in a ceiling tile will cause it to be highly reflective to UV-C whereas a white acrylic paint will hardly reflect any.

With upper air solutions you should also consider how the room is being used. For example, in a typical office it is unlikely that anyone will be standing in the exact spot where the maximum irradiance occurs for eight hours, so a calculation is also made for sitting and the total daily dose calculated.

Therefore for upper air systems we have to calculate both the fluence rate, which gives us the effectiveness of the disinfection, and check the safe dose for exposure.

It is recognised that air movement in a room will help disperse airborne viruses and often this is related to the air changes per hour (ACH). The basic ventilation rate required for fresh air, low CO2 and odour levels is mostly

Edeka store with UVGI mounted on the columns

accomplished with 1-6 ACH, sometimes up to 8 ACH. Opening windows gives 1-2 ACH, maybe higher, but with discomfort.

Increasing the basic ventilation rate significantly, for example, to ACH 15-20, is a well-known method to reduce pathogen levels for disinfection, especially in healthcare applications. Experiments with upper air UVGI solutions have shown that the disinfection achieved can be equivalent to 50 ACH (eqACH), providing there is basic air movement in the room to start with.

Equivalent ACH is related to average fluence rate by the following formula:

Eem x 3600 x k(λ)/1000 where k(λ) is the spectral susceptibility factor of airborne pathogens (sqm J1) and E e m is the average fluence rate (mW/sqm)

'Only the surfaces in direct sight of the UV-C source will be treated so anywhere where there are shadows will be missed'

Twitter: @sll100

In his paper Nardell3 proposes that the economic efficiency of UVGI is 9.41x that of ventilation for the same level of disinfection.

We have looked at the theory of how UV-C works and how you design an installation. But does it work in practice?

It's obviously impossible to pump the SarsCoV-2 virus into an occupied room, but you can measure the effect on naturally occurring fungi and bacteria and project the effect for Sars-CoV-2. The German food chain Edeka installed upper air UVGI in one of its outlets and independent tests were carried out by the Fraunhofer Institute4. Air-measuring devices were located around the store and the UVGI switched on and off on alternate days. During the time with highest customer use a fungal reduction of 50 per cent was observed. Given that the susceptibility of

Sars-CoV-2 is 20 times lower, they estimated that 99.99 per cent of the virus would be inactivated.

So what about the future? The current pandemic has highlighted the fact that clean air and good circulation will contribute to a reduction in airborne transmission. UVGI is another tool in our armoury in the fight against the spread of viruses. Although the focus has been on Sars-CoV-2, UVGI works on a wide range of pathogens including flu which returns seasonally. UVGI should not be thought of as simply a solution for now, but a permanent solution to help create healthy places where we can work, rest and play.

Mike Simpson, FREng CEng FCIBSE FSLL FILP FIET, is global application lead at Signify, and former SLL and CIBSE president

References 1 Rapid and complete inactivation of SARS-CoV-2 by ultraviolet-C irradiation. N Storm et al 2020 2 Efficacy of a wall-mounted UV device against aerosolised SARS-CoV-2. Innovative Bioanalysis. March 2021 3 Nardell: Air Disinfection for Airborne Infection Control with a Focus on COVID-19: Why Germicidal UV is Essential. 2021 4 Study on the evaluation of the efficiency of UV-C radiation as an air disinfectant during operating hours in a supermarket. May 2021

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UV lighting

November/December 2021

SUN PROTECTION Artist and innovator Daan Roosegaarde has turned UV-C into a social beacon for public spaces

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Images courtesy of Daan Roosegaarde

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The suspended (by crane) black sphere creates a 15m circle of far-UV-C light

The linear far-UV-C unit within the sphere

Daan Roosegaarde

V-C radiation is seen primarily as a utilitarian application, but Dutch artist and innovator Daan Roosegaarde, whose forte is marrying art and science in large-scale installations, has developed a concept that applies UV-C in outdoor public spaces to aesthetic as well as functional effect.

The Dutch artist and innovator, founder of what he describes as the social design lab Studio Roosegaarde, is known for projects such as Waterlicht, a well-travelled installation that evoked the power of water through light, and Smart Highway, where road markings are charged by the sun and glow at night.

The aim of Urban Sun, which began in 2019, is not only sanitation but to be a symbol of hope, a literal light in the darkness where people may gather. It is based on far-UV-C light, with a wavelength of 222 nanometers.

Roosegaarde argues that while traditional 254nm UV-C light can be harmful if the permitted exposure is exceeded (as with the Sun), far-UV-C light sanitises viruses such as the Sars-CoV-2 virus safely.

The Urban Sun’s source is measured and calibrated by the Dutch National Metrology Institute VSL and meets the International Commission on Non-Ionising Radiation Protection (ICNIRP) safety standards.

'The Covid-19 pandemic made the project much more urgent,' says Roosegaarde. 'Urban Sun connects design with science to provide innovative solutions to create spaces for people to meet and exchange in a safer and a more humane way. It can be exhibited in any type of public space and serves as a call to action to governments and partners to speed-up and upscale applications.' www.studioroosegaarde.net/project/urban-sun

Visualisation of skin cells and the difference in impact between traditional UV and less intrusive far-UV-C light

sll.org.uk

Health and wellbeing

November/December 2021

SEEING AND NOT SEEING Last month Dr Shelley James and Dr Denize Atan took part in an SLL webinar examining lighting for both the visual and non-visual systems. Here they outline their respective areas of concern – and highlight the need for research in both fields

HOW DOES LIGHT INFLUENCE EYE DEVELOPMENT? – Dr Denize Atan

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here is currently an epidemic in the prevalence of myopia (shortsightedness). By 2050, the World Health Organisation (WHO) estimates that half the world’s population, around 5bn people, will be myopic.

Myopia occurs in people who have longer than average eyes. This is because light entering the eye is refracted and focused in front of the light-sensitive retina, instead of directly on to it, causing distant objects to appear blurred

Twitter: @sll100

while close objects appear clear. Although the symptoms of myopia can be corrected with glasses, contact lenses or laser eye surgery, people with longer eyes are more at risk of potentially blinding complications, such as retinal detachment and glaucoma. Hence, myopia is now the commonest cause of visual impairment in the world.

While the genes we inherit can influence our chances of becoming myopic, there is also evidence that our increasingly urbanised lifestyles over the past 100 years have contributed to the current myopia epidemic far more than genetics. Essentially, children need to spend at least one to two hours outside every day to develop healthy eyes and vision, because when the retina is exposed to natural daylight, it signals the eyes to stop growing beyond their normal limits. It is, therefore, concerning that British children are now spending much more of their day on devices

such as computers, tablets and phones, and less time outside than ever before. What we really need to find out is whether certain types of indoor artificial lighting could protect against myopia to the same extent as natural daylight.

However, this needs further research into how the brightness, wavelength and flicker of artificial light can affect eye growth and visual development.

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Health and wellbeing

November/December 2021

HOW DOES LIGHT INFLUENCE THE BRAIN?

– Dr Shelley James

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very single cell in your body and brain is responding to light, from your skin to your brain stem.

We share this photosensitivity with every living thing on earth, from plankton to plants.

The human visual system not only perceives brightness and contrast, it also evolved to notice colours too. Scientists believe that colour-sensing developed for two vital reasons, the first, to aid social interaction: changes in emotion are expressed in subtle changes in the blood flow – and the colour – of the face. The second is to identify different foods and their state of ripeness.

Until around 20 years ago, we believed that the eye simply collected light and processed that stream of signals along the optic nerve, through the visual cortex and on through a series of filtering and interpreting stages to create our experience of ‘vision.

But scientists noticed that people who were functionally

'There is an urgent need for research that translates laboratory findings to the real world'

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blind seemed to be able to ‘tell’ when to go to sleep and when to wake up. They discovered a second pathway that has become known as the ‘non-visual’ pathway that responds to slow changes from day to night, particularly the presence, or absence, of the bright ‘blue’ wavelength (480nm) that is dominant in morning sunlight. This is also the main wavelength given out by computer and mobile phone screens as well as the vast majority of LED sources.

This simple, reliable and powerful ‘time switch’ can be seen as the conductor, activating every single cell in the body in a finely tuned and highly effective sequence. Disruption to this body clock by exposure to those ‘wake up' wavelengths after dark has been linked to a growing number of conditions from cancer and heart disease to obesity and depression.

Equally, these bright ‘cool’ wavelengths can be used to improve attention, memory and mood. A burst of bright light can be more effective than a double espresso in cutting reaction times and increasing short-term memory. Exposure to bright light for 80 minutes in the morning has been shown to reduce suicide rates. And a growing number of care homes are using lighting to cut sundowning and cognitive decline, and reduce pharmaceutical pain relief.

The colour response, although subtle, is also a powerful cue. A growing body of evidence suggests that light sources which provide the full range of wavelengths that mimic the spectral distribution of sunlight not only improves visual comfort and the ability

to respond appropriately to others, but it also affects the quality of sleep and even the healthy development of the eye itself.

Finally, the growing sensitivity of tracking devices is shining a light on the impact of flicker on the brain, particularly for vulnerable groups such as those with ADHD and autism.

Flicker rates up to 1000 times the flicker fusion threshold of around 120 cycles per second have been shown to trigger a cascade of responses in the cerebellum that is implicated in behavioural issues in people with autism.

This is an exciting time to be working with light. Current research points to a number of powerful benefits of light – including artificial light – for visual, mental and physical health.

However, there remains an urgent need for research that translates laboratory findings to the real world.

Dr Denize Atan is senior clinical lecturer at Bristol University and an honorary consultant in neuro-ophthalmology at the Bristol Eye Hospital. Dr Shelley James is a lumenologist and founder of specialist light consultancy Age of Light Innovations www.ageoflightinnovations.com www.bristol.ac.uk/medical-school/about/ profiles/denize-atan/ Lighting for the Eye and Brain, an SLL webinar, took place on 21 October from the Life Sciences Building, Bristol. To see the webinar go to: www.cibse.org/society-of-light-and-lightingsll/sll-events/pastpresentations

sll.org.uk

LR&T essentials

November/December 2021

A MEASURED APPROACH Limiting damage to art and the assessment of metrics are the subjects of the three latest Lighting Research and Technology papers, discovers Iain Carlile

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argano et al have investigated the lighting of artworks, examining how to display them while also limiting the potential damage caused by long-term exposure to light. The authors used different projection systems (slide and video), together with filters to apply a selective chromatic lighting technique, effectively projecting an image of a two-dimensional artwork on to itself, allowing lower illuminance levels to be used without sacrificing luminance.

They found that this was an efficient way of modifying the spectral distribution of light sources, enabling removal of the wavelengths of light most strongly absorbed by the artwork, thereby reducing potential damage and enhancing the visibility of the artwork. It was also found that the LED projectors, in combination with photographic or transparency slides, provided the best enhanced spectral emission of the projector systems investigated.

The authors note that while their proposed system reduces potential damage of artworks and increases visibility, the study did not consider viewers’ perception of the artworks illuminated using this method.

Durmus’s paper looks at the use of CCT as a lighting metric, its use and limitations.

Durmus notes that although CCT is a simple to understand metric used to quantify the perceived colour of electric light sources, due to the limitations of its one-dimensional nature its use in scientific research may be inadequate. Durmus recommends that for repeatability and accuracy of research experiments, other information needs to be recorded by researchers, including: detailed light source characteristics, absolute spectral

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Schematic representation of the principle of the proposed method: white and selective coloured light projection system (Gargano et al)

power distributions with radiometric quantities, and Duv, which is defined as: 'the distance from the chromaticity coordinate of the test light source to the closest point on the Planckian locus on the CIE 1960 (u,v) UCS, with a plus sign for above and a minus sign for below the Planckian locus.' For visual experiments it is also recommended to record the environmental conditions, chromatic adaptation duration, and interobserver differences.

'The development of the lighting profession toward the third stage requires our attention shifting from the light on certain planes to the light distributions in 3D spaces,' contend Xia et al, in a reference to proposals initially put forward by Kit Cuttle in recent years.

The authors propose a practical strategy to measure the local density of illumination in 3D scenes. This is based on the zeroth-order of spherical harmonics (SH) decompositions of a high dynamic range (HDR) panoramic map, which they refer to as illuminance panoramic.

Measurements were simulated in a model and verified using six HDR panoramic maps of real scenes. The results showed that the measurements coincided well with its definition (the average illuminance over a sphere). The authors suggest that this method could be developed for use with mobile devices as a tool to measure the density of illumination in threedimensional spaces.

Iain Carlile, FSLL, is a past president of the SLL and a senior associate at dpa lighting consultants

Lighting Research and Technology: Online First 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) A new lighting method for cultural materials using selective chromatic light M Gargano, S Scotuzzi, EM Angelin, O Santilli, JM del Hoyo-Meléndez, N Ludwig Correlated colour temperature: Use and limitations D Durmus Theory and simulation of calculating local illuminance density based on high dynamic range panoramic maps L Xia, R Xu, T Zhang, X Liu

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Events

2021/2022

For details of all upcoming webinars, go to: www.cibse.org/society-oflight-and-lighting-sll/sll-events/upcoming-webinars-and-online-content For previously recorded CPD webinars (including regional webinars), go to: www.cibse.org/society-of-light-and-lighting-sll/sll-events/pastpresentations

EVENT LIGHT + BUILDING 2022 Venue: Messe Frankfurt Date: 13-18 March 2022 www.light-building.com

ONLINE EVENT SHAPING LIGHT FOR HEALTH AND WELLBEING IN CITIES (International Conference organised by the ENLIGHTENme Consortium, an EU project) Date: 16-17 December 2021 www.enlightenme-project-conference.com

AVAILABLE WEBINARS INCLUDE INDOOR LIGHTING: CHANGE IS AFOOT (SLL and CIBSE Ireland) Looking at the newly revised BS EN 12464-1:2021 Light and Lighting of Work Places. Part 1. Indoor Workplaces, launched this autumn.

Speaker: Sophie Parry, FSLL, technical applications consultant for ZG Group UK and Ireland, and chair of the SLL technical and publications committee THE VISION (SLL and CIBSE Ireland) The presentation explores the evolution of our cultural relationship with light and darkness while taking a closer look at the theme of environmentally friendly lighting through case studies.

Speaker: Kerem Asfuroglu, founder of Dark Source, a lighting design practice focusing on social and environmental values DELIVERING THE CIRCULAR ECONOMY FOR THE LIGHTING INDUSTRY (SLL and CIBSE Home Counties South West) Chair: Hakeem Makanju, CIBSE HCSW regional chair, and David Mooney, SLL representative for HCSW Speakers: Bob Bohannon, FSLL, SLL immediate past president; Kristina Allison, CEng MCIBSE MSLL, chair of the SLL education and membership committee; Roger Sexton, FSLL, business development for Stoane Lighting; Tim Bowes, MSLL, head of lighting application for Whitecroft Lighting

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