SLL Mar/Apr 18

Newsletter Volume 11. Issue 2. March/April 2018

The Society of Light and Lighting

Part of the Chartered Institution of Building Services Engineers

A TASTE OF LIGHTBYTES

Topics from the Lighting Knowledge Series

BROADER VISION

Challenging a traditional metric @sll100

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Editorial

Secretary Brendan Keely FSLL bkeely@cibse.org SLL Coordinator Juliet Rennie Tel: 020 8675 5211 jrennie@cibse.org Editor Jill Entwistle jillentwistle@yahoo.com Communications committee: Gethyn Williams (chairman) Rob Anderson Iain Carlile MSLL Jill Entwistle Chris Fordham MSLL Eliot Horsman MSLL Mark Ingram MSLL Stewart Langdown MSLL Linda Salamoun MSLL Bruce Weil 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 NL 3 2018 is 23 March Published by The Society of Light and Lighting 222 Balham High Road London SW12 9BS www.sll.org.uk ISSN 1461-524X © 2018 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

Produced by

Printed in UK

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Unit C, Northfield Point, Cunliffe Drive, Kettering, Northants NN16 9QJ Tel:01536 527297

One of the great benefits of the lighting technologies which have developed over the past 20 years or so is that they allow an enormous amount of flexibility, which can bring both cost and energy savings, as well as, in theory, health and wellbeing improvements such as biodynamic lighting.

The controllability of LEDs combined with ever more sophisticated ways of controlling them has enabled, most obviously, greater energy efficiency.

Linked with daylight and/or presence/ absence sensors, the lighting should never be on unnecessarily.

By the same token occupants should appreciate colour temperatures morphing

from cool white to warm white according to the time of day.

But still buildings shine out like lighthouses at night (and not because they’re on the cleaning setting) and controllable curtains still remain up or down rather than where they’re supposed to be to fulfil their function.

And more than one specifier has admitted that the biodynamic system that has been installed at some expense actually remains on the same colour temperature setting.

One always has to factor in a degree of apathy wherever human beings are gathered together but there are other reasons. One is that people can still find control systems intimidating and those panels can look a bit scary for the nontechnologically inclined. Another reason can be that no one has fully explained what the control system can potentially do or possibly even how to operate it.

Commissioning Code L, now in a new edition (see p14), is specifically designed to ensure that the finished installation actually fulfils its design promise and not only functions correctly but continues to operate as intended. There’s little point in having all this whizzy technology if it is not exploited to the full.

Jill Entwistle jillentwistle@yahoo.com

Current SLL lighting guides

SLL Lighting Guide 1: The Industrial Environment (2012) SLL Lighting Guide 2: Hospitals and Health Care Buildings (2008) 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 (2015) 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 (2014) SLL Lighting Guide 14: Control of Electric Lighting (2016) LATEST SLL Lighting Guide 0: Introduction to Light and Lighting (2017) SLL Lighting Guide 15: Transport Buildings (2017) SLL Lighting Guide 16: Lighting for Stairs (2017) Guide to Limiting Obtrusive Light (2012) Guide to the Lighting of Licensed Premises (2011) Commissioning Code L (2018)

Secretary’s column

‘What better way to celebrate the world of light than to be present at the LR&T Symposium on 16 May, the inaugural Unesco International Day of Light?’

Editorial 2 Secretary’s column

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News 4 A taste of LightBytes 5 Three speakers from the Lighting Knowledge Series give a flavour of the topics covered Well beyond target 9 Arup lighting director Arfon Davies on the lighting scheme for the company’s own Boston office which focuses on the health and wellbeing of its occupants Does Vλ SPD measure up? 11 David Loe and Peter Raynham challenge the traditional metric with a pilot experiment Work on commission 14 The new Commission Code L has been revised and rewritten to address the issues of ever evolving technology Body clock watching 15 Iain Carlile finds that the effect of lighting on circadian rhythms is a key subject in the latest online LR&T papers Events 16 Cover: Entre Les Rangs by Rami Bebawi/KANVA, at King’s Cross, one of the installations at Lumiere London 2018

Matthew Andrews

The 50th Volume: Issue 1 of Lighting Research and Technology is now available to all members to download or purchase in hard copy. The journal presents papers from the world’s leading researchers in light and lighting. Many of the contributors to this special edition will be presenting at the LR&T 50th Volume Symposium on 16 May (see News p4), coinciding with the inaugural Unesco International Day of Light.

What better way to celebrate the world of light than to be present at the event?

The presenters will give a brief overview of their papers and then discuss the future of light and lighting in their specific fields of research.

It will be a brilliant and highly informative day and I hope that many of you can join us at the Darwin Building at UCL, London. Booking for the event can be made through the SLL website.

Anyone who would like to purchase the special edition of LR&T can do so by contacting the publisher, Sage Subscriptions Department (subscription@sagepub.co.uk).

We are coming close to the entry

deadline for the Young Lighter of the Year 2018 applications. The Young Lighter competition provides an opportunity for all under 30 on 11 May 2018 to demonstrate their passion for light.

The potential subjects for presentations are a lot broader than a lot of people realise. They don’t have to be centred on academic research, for instance.

The paper could be on a project you’re particularly pleased with or that was challenging, or it could be about product design or your experience of the lit environment around you. It could even be about photography – after all, it’s still about light. You will have a chance of winning the title Young Lighter of the Year and £1000. Entry details can be found on the website.

The 16th annual Ready Steady Light competition, in collaboration with Rose Bruford College, is almost upon us (13 March) and we encourage all to enter this fun and creative event. Last year the technical award was won by WSP Parsons Brinckerhoff, the artistic award

by Light Bureau and the peer prize by Future Designs.

We look forward to meeting with our supporters at Light + Building in Frankfurt later in March. It’s our opportunity to thank the supporters in person and ensure they are maximising their benefits. We have some free entry codes to the exhibition so if you are heading there please do get in touch with me and I can pass them on.

The Lighting Knowledge Series: LightBytes (see p5) has been very well received this year and there are still three of the seven events left in the calendar.

On 26 April we’ll be in Newcastle, on 10 May in Glasgow and on 7 June in London. The series, supported by Fagerhult, Trilux, Xicato and Zumtobel, replaced the Masterclass events with new presentations based on the themes of Design, Specify, Build and Future.

The society’s AGM, awards and presidential address is set for 24 May at the Haberdasher’s Hall in London EC1.

It will be a celebratory evening where we get to acknowledge the work of the brilliant volunteers as well as introduce the new president, Iain Carlile. We hope you will be able to join us.

Contents

Brendan Keely bkeely@cibse.org For up-to-date information follow us on Twitter @sll100

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NEWS...NEWS...NEWS...NEWS...NEWS...NEWS...NEWS...NEWS...NEWS...NEWS...NEWS...NEWS...NEWS...NEWS...

LR&T Symposium lines up top researchers as speakers

The LR&T Symposium, to be held on the inaugural International Day of Light on 16 May, will feature a line-up of prominent researchers, all contributors to the special 50th volume.

Among them will be Mark Rea (far left) and Mariana Figueiro from LRC who will look at The Where and What of Lighting Vision Research, and Non-Visual Effects of Light respectively. The keynote speakers will be Mike Simpson (second left) and Peter Boyce.

Other speakers will include John Mardaljevic (third from left), professor of Building Daylight Modelling at Loughborough University, Arnold Wilkins, director of the Visual Perception Unit

Sheffield hosts next science and technology event Registration is now open for the 16th International Symposium on the Science and Technology of Lighting on 17-22 June 2018 at Sheffield University.

The event is organised by the Foundation for the Advancement of the Science and

On the lighter side...

From the outfit that brought us the Banana lamp, the Monkey lamp and the Mouse lamp comes the cat lamp, or Felix as it’s known. Dutch design duo Studio Job and Italian design brand Seletti have created a life-size dimmable resin luminaire with a USB port. Rechargeable, Felix comes in three different versions: black, white, and a spotted black and white. It costs around £200. You really don’t want to know where you plug in the USB or how it’s dimmed.

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at the University of Essex, and Steve Fotios (far right), professor of Lighting and Visual Perception at Sheffield University’s School of Architecture.

The one-day event will be held at the Darwin Building at UCL, London. It will run from 10.30am to 6pm (registration starts at 10am).

The 50th Volume: Issue 1 of Lighting Research and Technology is now available. Members can download it free of charge or purchase a hard copy (£17).

For more details of the symposium go to sll.org.uk, and to get a copy of LR&T Vol 50 Issue 1 go to subscriptions@sagepub.co.uk Technology of Light Sources (FAST-LS) in conjunction with The Centre for GaN Materials and Devices at Sheffield.

The now biennial event dates back to 1975 and is held at different international locations. It aims to provide a forum for scientists and engineers worldwide, in both academia and industry, to share and exchange the latest progress on the science and technology of lighting.

For more details go to www.ls16.org

Global study launched on urban IoT The London School of Economics, LUCI (Lighting Urban Community International) and Osram have launched a global, comparative study of municipal smart lighting.

Pathways to Municipal Smart Lighting aims to show how cities and towns worldwide understand intelligent lighting, how the topic fits into visions and plans for the future urban environment, and how smart lighting can be realised within the framework of specific public policies.

Through a global city survey and detailed case studies of five selected municipalities, the project will explore how different cities and towns are managing policy, implementation and governance of smart lighting.

The move to smart lighting will involve convergences of infrastructure, data and control, with potentials of efficiency, cost savings and improvements in the quality of life, says the study group.

‘However, “smart” means radically different things to municipalities and their stakeholders across the world – different technologies, development strategies and governance policies,’ adds the group.

The project aims to clarify the motives, objectives and expectations driving the demand for smart lighting. It will also compare challenges and opportunities for cities worldwide, and provide information on which strategic routes municipalities will follow in the future with their intelligent lighting.

The Configuring Light research group – part of LSE Sociology and affiliated to LSE Cities – will be carrying out design and realisation of the research project.

The aim is to present the results at the LUCI AGM in November this year.

Lighting Knowledge Series 2018

A taste of LightBytes

Each speaker in the LKS takes the themes Design, Specify, Build, Future in a series of short presentations. To give a flavour, three speakers take one of those themes each and briefly outline the issues covered

LightBytes: Design Roger Sexton

‘A light’s white appearance can have a big impact on how we experience it, our health, and the impression we get when observing our environment’

The way we experience artwork is strongly dependent on the white appearance of its illuminant, here illustrated with two Chinese paintings lit by cool and warm light sources respectively

Our day/night clock is regulated by the blue content in light, which is associated with its correlated colour temperature.

To suppress melatonin production – the hormone that makes us sleep – light with a high correlated colour temperature is needed, which is provided by daylight in nature in large quantities. To activate melatonin production, and to prepare us for sleep, we need lower light levels and light with low blue content, such as that traditionally provided by fire and candles, and (dimmed) incandescent light bulbs. If artificial lighting needs to be used during the day in the absence of daylight, it is important to provide the right light levels and white appearance to regulate natural wake/sleep cycles.

The way we experience works of art is strongly dependent on the white appearance of its illumination. Figure 1 shows an example of two Chinese paintings, lit with a cool and high correlated colour temperature on the left and with a warm light source with a low correlated colour temperature on the right.

The illumination with the cool white is more fitting than the warm-white illumination. The opposite would be true for, say,

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The starting point of any lighting design is with the light itself, regardless of whether it originates from an LED, or traditional fluorescent or halogen lamps. Light varies in ways which designers need to be able to quantify, hence the need for metrics. The two most critical metrics for a source are its white appearance and colour rendering quality.

The appearance of white – commonly expressed by words such as ‘warm’ or ‘cool’ white and combinations of these – is technically characterised by its colourimetric white point, and measured by colourimeters. This white point is in practice expressed by its correlated colour temperature and distance to the blackbody locus. The tungsten filament in a traditional light bulb typically operates at a physical temperature of around 2850 Kelvin (K), when it produces the white light we know so well, and which we call ‘warm’. If tungsten could be heated even more, to temperatures of 5000K and 6500K, its emission would turn blueish, and become similar to the light emitted by the sun – the colour of light we call daylight.

A light’s white appearance can have a big impact on how we experience it, our health, and the impression we get when observing our environment: looking at artworks, for example, or perhaps making accurate differentiations in surgery. A source with a relatively low correlated colour temperature, such as from a candle or fire, we describe as warm, probably because it is associated with fire, and the fact that an incandescent bulb produces infrared light as well as visible light, which warms us up through radiative heat. And light with a high colour temperature we counterintuitively describe as cool – the temperature of daylight, for example.

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Lighting Knowledge Series 2018

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TCS 01 - light greyish red 7.5R 6/4 TCS 02 - dark greyish yellow 5Y 6/4 TCS 03 - strong yellow green 5GY 6/8

TCS 09 - strong red 4.5R 4/13

TCS 04 - moderate yellowish green 2.5G 6/6

TCS 10 - strong yellow 5Y 8/10

TCS 05 - light bluish green 10BG 6/4

TCS 11 - strong green 4.5G 5/8

TCS 06 - light blue 5PG 6/8

TCS 12 - strong blue 3PB 3/11

TCS 07 - light violet 2.5P 6/8

TCS 13 - light yellowish pink (skin) 5YR 8/4

TCS 08 - light reddish purple 10P 6/8

TCS 14 - moderate olive green (leaf) 5GY 4/4

BASE TEST COLOUR SAMPLES

EXTENDED TEST COLOUR SAMPLE SET

The approximate colours of the test colour samples as used in the CIE CRI (colour rendering index) standard

The colour evaluation samples used in determining the colour fidelity and colour gamut indices in the TM30 standard

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Individual colour fidelity values for each of the colour evaluation samples for a standard fluorescent lamp (CIE F3 standard illuminant) and a high colour fidelity LED source

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17th-century Dutch paintings, for which warm-white or low correlated temperature illumination is more appropriate.

Also the potential damage of artwork due to light is correlated with white appearance: light with a high correlated temperature typically has a high blue content. It is especially the blue light, consisting of photons with more energy, which is more damaging. A damage factor, for example, as defined in CIE report CIE 157:2004, can be calculated and used to determine how long a piece of art can be exposed before it starts to show colour deterioration.

Besides the white appearance of the light itself, its spectral composition is important, in particular when we want to see the colours of objects correctly. The colours of an object we see are associated with the wavelengths contained in its illuminating spectrum, and reflected and filtered by its material, which might contain, for example, pigments and other colourants. If certain wavelengths are missing or more pronounced in the light, they will be missing or be more pronounced in the reflected light as well, in which case the colour appearance of an object will be off.

The capability of a light to render colours correctly is characterised by one or more colour rendering indices. As a basis for colour rendering, index patches of representative reference colours are taken. For each of these patches two colour points are measured or calculated: one colour point represents the colour of the object when illuminated with the light source under evaluation, and the other colour point represents its colour when illuminated with an ideal reference light source. As a reference source either a Blackbody radiator, a standard CIE daylight illuminant, or a combination of both is used.

There are a couple of different colour rendering standards.

Traditionally the CIE 13.3 1995 or CRI standard is used, but it has some weaknesses and recently some new standards have been proposed and adopted. The new IES TM-30-15 or TM30 standard in particular fixes many issues from this older standard.

Colour differences between the evaluation and reference source don’t necessarily have to be bad. In theatre and architectural lighting design, for example, using light to enhance or accentuate the colour of objects can be a useful tool. For this purpose it is beneficial to distinguish colour rendering quality in colour fidelity perfomance and colour preference performance.

The CIE CRI standard only covers colour fidelity performance, while the TM30 standard includes both fidelity and colour preference metrics. The colour preference metric in the TM30 standard is called the gamut index.

The CIE has started to adopt the improvements from the TM30 standard: a first step comes in the form of CIE 224:2017 Technical Report: CIE 2017 Colour Fidelity Index for accurate scientific use.

The technical committee for this report (TC1-90) did not make the step yet to officially replace the CRI metric CIE 13.3.1995, so for now the TM30 is arguably the best metric for colour rendering.

Roger Sexton is vice president specifier services at Xicato

Lighting Knowledge Series 2018

LightBytes: Build Steve Shackleton

There is a significant body of evidence which suggests that many buildings are not performing as intended. The final phase of the build, often squeezed into the last days on site and often seen as a buffer period for overrunning works, is arguably the most important – commissioning. This is the make or break point.

But what actually is commissioning and what does it mean for lighting? Along with to order or to authorise the production of (something), commission a painting or appoint (someone) to the rank of officer in an army, navy, or air force, or indeed for some people part of their earnings, the definition of commission in our sense is to bring something newly produced into working condition. Interestingly, the use example given in the online dictionary was ‘we had a few hiccups getting the heating equipment commissioned’.

In the case of lighting, or perhaps more accurately lighting controls, commissioning is often limited to addressing luminaires, setting scenes and adjusting time-out periods on presence detectors, and arguably that is indeed bringing something new into working condition. But the evidence suggests that we likely need to do a great deal more. Perhaps, in a lighting sense, we need to revisit what we actually mean by the term commissioning:

Are the specified products installed?

Are the specified products installed in the right places?

Light meter readings. I have a colleague in the industry who has worked in a particular sector of lighting where many large projects are undertaken. To be successful on such projects, potential suppliers must jump through burning hoops of fire to be considered, undertaking a stringent technical and commercial selection process. And yet, after the dust has settled, apart from occasional instances of sample illuminance checks in some critical areas, checks are seldom made and there is no track record of checking reflectances of surfaces, colour temperature, colour rendering or even actual wattage The vast majority of installations don’t seem to be subject to anything like the level of scrutiny post-installation, as they are pre-order, and I wonder why that is.

It could be to do with cost: while there are dozens of smartphone lightmeter apps available of questionable accuracy, a professional cosine and colour-corrected light meter will likely cost from £1000 upwards, and a sufficiently trustworthy colour meter might start at £2000. And that doesn’t include the time involved, which in mid-summer can certainly be classed as unsociable hours.

It could also be to do with our tolerance of light. Arguably it is easy, in many situations, to provide light that is adequate, acceptable, good enough – and in some circumstances that might well be good enough. By the same token it is actually quite difficult to ‘achieve’ lighting that is genuinely bad. Maybe we have settled on lighting commissioning as ‘it looks ok’ as good enough...

Interestingly, Commissioning Code L (L for lighting) has just been published (see p14) and includes many of these themes.

Are the specified products properly adjusted?

Steve Shackleton, FSLL MILP, was formerly technical director Northern Europe of the Zumtobel Group

Are the specified products performing as predicted?

Are the controls performing as predicted?

Are the controls settings suited to the real occupancy of the building?

Do the factory settings take account of the season?

So, in summary,is the installation performing as predicted?

LightBytes: Future Helen Loomes

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What is the future for lighting manufacturers? Times are changing and so will the ultimate responsibility of any conscientious manufacturer. If embraced, the new challenges can provide exciting prospects.

If we look at some trends in the lighting market we might see where they are leading us. To understand how quickly things are changing, we should look first at some other industries.

Smartphones have been adopted at an alarming speed and now everyone has a camera in their pocket and pictures can be shared instantly.

Flat panel TVs have saturated the market in only a few years.

Old technology cathode ray tubes are no longer available. Like LEDs, these developments are disruptive technologies.

In the past lighting technology did not move fast. Take @sll100

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Lighting Knowledge Series 2018

‘We are used to this with our phone contracts. When a new model comes out, a contract allows the user to upgrade – why not do something similar with lighting?’ t

fluorescent lamps, for example. The tube diameter reduced from 38mm to 26mm at the end of the 1970s, compact lamps appeared in the mid-1980s and the 16mm diameter tube was introduced in 1997. All these changes were no more than improvements of an existing technology.

LEDs are different and have completely transformed the face of the lighting industry from a number of perspectives, from the type of companies who have entered the market (Asian electronics giants, for instance) through to the different approaches to lighting the technology has enabled.A lot of advantages have resulted in a complete switch over to this new technology within a relatively short time. LEDs and the controls technology they facilitate are here to stay,and many new features and facilities are now already used and accepted:

Dimming is commonplace. LEDs can be dimmed more easily Dali has become a standard protocol Sustainability is getting more and more important,

and energy savings are promoted by our regulations

Daylight-linked systems and presence detection are commonplace

Light management systems are also being used for a variety of functions beyond simple regulation of lighting:

To improve the use of buildings by giving data on usage.

Heat mapping can show that one part of your warehouse is regularly visited; why not move those goods nearer the front and reduce effort?

possibly with a personal element. Manufacturing systems will rely on digital input, just-in-time deliveries and very little stock holding. But there might be new ways of making a profit – data has become a very valuable commodity. Companies such as Apple could be delivering the lighting in future, while LiFi, whereby the lighting system becomes a data conduit, has become a reality.

When you consider the sum of these parts it leads us to a new approach. To focus on just one possibility, perhaps the manufacturer should be selling a service – renting light. Clients don’t need to know the price of an individual luminaire, they just wants the right light when they need it, for a monthly fee.

This should be a turnkey solution – the client doesn’t want any problems, and even design responsibility could be covered by the professional indemnity of the service provider. But how much? Where does the liability end? Perhaps this could be turned around and used to our advantage.

We are used to this with our phone contracts. When a new phone model comes out, a phone contract allows the user to upgrade – why not do something similar with lighting?

One complication is life-cycle costs. But knowing that you produce a superior quality luminaire, you offer replacements and offer to extend your warranty, thus saving the contractor money and, again, you calculate in the risk factor.

Light management systems result in only using the lighting when it is needed, so it is up to service providers to calculate this correctly and tune the profit, because they are paying the energy provider. The maintenance can be planned on the basis of information fed back from the system and the manufacturer can decide when is the opportune moment to upgrade to a more energy-efficient system paid for out of energy savings.

This brings in a range of new business partners (installers, financers, project managers, project developers).

From a manufacturer’s point of view it has financial issues. It is the transference of risk. Manufacturers will have full responsibility even at the end of the product’s life under the WEEE directives.

One thing is certain and that is we have to start thinking about it now. The lighting industry is no longer just about making light fittings – we have become solution providers.

Helen Loomes, FSLL, is business development director, international sales at Trilux Lighting

To predict maintenance cycles and life (which could have a bearing on warranties)

To carry other data The first Industrial Revolution used water and steam power to mechanise production. The second used electric power to create mass production. The third, the digital revolution, used electronics and information technology to automate production.

Now a fourth revolution has evolved from the digital revolution.

It is characterised by a fusion of technologies that blur the lines between the physical, digital and biological spheres, and all happening at breakneck speed. Think robotics, artificial intelligence, nanotechnology, quantum computing, biotechnology, 3D printing and autonomous vehicles.

Disruption is occurring in almost every industry in every country. And the breadth and depth of these changes herald the transformation of entire systems of production, management and governance – and perhaps ethos? Business models will become tightly controlled and focused on delivering new products quicker, they will have shorter life cycles,

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The remaining LightBytes events will be: 26 April, Newcastle 10 May, Glasgow 7 June, London See Events (p16) or go to the website (sll.org.uk) for more details. The Lighting Knowledge Series is supported by Fagerhult, Trilux, Xicato and Zumtobel

Darren Scott Hunter

Well beyond target

A year ago, Arup’s Boston staff relocated from an old building in Cambridge, Massachusetts, to a 1115sqm space on the 10th floor of 60 State Street in Boston just steps from the city’s historic Faneuil Hall. The building is a 38-storey steel-andglass tower designed by Skidmore, Owings and Merrill in 1977 and features unusually large windows that provide expansive views of the harbour as well as downtown Boston.

Arup’s lighting team worked on the lighting scheme for the new office, which aimed both to improve occupant satisfaction and achieve a WELL Certification, creating a lighting

environment that focused on occupants’ health and wellness.

Tuneable lighting was integrated into the design, with every office luminaire programmed to change colour temperature, aligning the ambient condition of the entire space with the sun.

The use of tuneable lighting was also extended beyond the office areas to include all lighting within the new office area (for example meeting rooms, break-out areas and circulation).

Guided by an astronomical time-clock, which accounts for seasonal changes in sunrise and sunset, the office lighting transitions from 3000K in the morning to 5000K in the midday hours and then returns to 3000K in the late afternoon. Natural and electric light are blended together, reinforcing occupants’

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Based on his presentation for the recent Build2Perform event, Arup’s lighting director Arfon Davies evaluates his own company’s lighting scheme for its new Boston office with its focus on occupants’ health and wellbeing

‘Natural and electric light are blended together, reinforcing occupants’ circadian rhythms’ Top: Tuneable lighting was integrated into the design and extended beyond the conventional office areas to include spaces such as meeting rooms, circulation and break-out areas

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Health and wellbeing

Left: colour-changing differentiates casual dining areas from workspaces

Darren Scott Hunter

Below: workstations and common areas are located near the windows to take full advantage of natural light

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circadian rhythms. Incredibly, this innovative lighting system only uses 0.67W per square foot (0.09sqm), which earned Arup a rebate from the local power utility.

Workstations and common areas are located near the windows to take full advantage of natural light. However, the quality of daylight inside the building is quite diminished by the heavy tint of the existing glazing. Arup’s lighting team worked closely with the architects to balance the low quality of the daylight and add brightness to the space, keeping lines clean and the ceiling uncluttered to make sure the ceiling would be the main ‘light source’.

Linear pendant luminaires are centered on the structural bays, rather than the furniture systems, reinforcing the symmetry and repetition of the building’s structure and also allowing for future reconfiguration. The pendants provide an even wash of indirect white light on the ceiling, creating a uniformly rich lighting environment and making the space feel more voluminous than it is. (The pendants offer 85 per cent indirect illumination to limit glare.)

The lighting design exceeded WELL’s requirements, with the office becoming the first WELL-certified project in New England and the 14th in the world to achieve Gold Certification (even though Arup’s target was Silver). The lighting design also achieved its objective to improve occupants’ satisfaction.

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Darren Scott Hunter

‘It took Arup months to get every layer of light working as it should, often a result of a sharp learning curve due to working with new technologies’

For instance, 74 per cent of the occupants were satisfied with the new lighting compared to 35 per cent in the old office; 72 per cent felt the office environment was inspiring and energising (vs 38 per cent), and 94 per cent felt proud to bring visitors to the office, whereas only 33 per cent felt comfortable doing so in their old building.

Although this project has surpassed everyone’s expectations, a level of fine tuning was needed. The use of tuneable lighting beyond the work areas to encompass all lighting within the office required the integration of a wide range of different technologies within a single control system.

It took Arup months to get every layer of light working as it should, often a result of a sharp learning curve due to working with new technologies. The result is, however, a unified lighting design, which goes beyond the standard tick-box tuneable lighting system, providing an environment that is blended and connected to the sun throughout the office.

Lighting metrics

Does Vλ SPD still measure up?

‘Mankind has been around for many thousands of years with only daylight illumination. Therefore it would seem strange that the eye has only a limiting spectral response, as with the Vλ SPD’

Courtesy of Peter Tregenza

the comparison of the Vλ SPD and a typical daylight SPD, though the latter can vary slightly depending on the time of day and the system of measurement.

The hypothesis is that the fovea may have a spectral response of Vλ, but human vision covers a much larger spectral range and hence colour sensation may be experienced in the para-foveal region of the eye, together

Fig 1: electromagnetic spectrum described by wavelength in metres together with the human visual spectrum and the CIE photopic Vλ spectral distribution

Courtesy of the NPL, UK

Human sight responds to electromagnetic radiation which enables us to see over a range of approximately 400-700nm.

This creates the visual experience of different colours. Yet we measure light on the basis of the CIE photopic spectral power distribution (SPD), labelled the Vλ distribution, which was agreed internationally in 1924. However, this assesses the effectiveness of light differently across the visual range on the basis of the measurement of the spectral response of the human eye (see Fig 1).

In the early part of the 20th century when electric light was being introduced there was a clear need to have an internationally agreed standard by which all light sources and illumination were measured. At that time there were no regularly available photoelectric systems of measurement and so the measurements were made by visual comparisons using optical instruments with a very narrow field of view.

This meant that the results, if correct, only applied to the central area of the visual field, the fovea, a conical field of around two degrees in diameter. This is the area of human vision which has the highest concentration of light receptors.

However, the eye sees over a much larger field, a cone of around 100 degrees in diameter. Since then there have been a number of studies to check the Vλ distribution with results similar to the original finding.

At this point we should consider human evolution. Mankind has been around for many thousands and thousands of years experiencing only daylight illumination. Even the discovery of flame sources is a few thousand years ago. Therefore it would seem strange that the eye has evolved with only a limiting spectral response, as with the Vλ SPD. Fig 2 shows

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The method of assessing the effectiveness of light was established in 1924.

David Loe and Peter Raynham continue the discussion on the validity of this traditional metric with a recently conducted pilot experiment

Fig 2: CIE photopic spectral power distribution (SPD) shown as a bell-shaped curve with the peak at 555nm, together with the SPD for daylight for both clear sky (full line) and cloudy sky (dotted line)

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Lighting metrics

t

Photos courtesy of Peter Raynham

‘Using the Vλ approach distorts the measurement of a lamp’s SPD and would affect the lamp efficacy. It could also affect the colour appearance and colour rendering classification’ with the fovea. And that the colour experience and the visual sensitivity, depending on the particular requirement, somehow combines the information of the two areas. To determine this requires the measurement at least of the colour response of the para-foveal region which will depend on an input of ophthalmologists and neurologists.

Pilot experiment In recent times lighting practitioners have been interested in luminance distributions, luminance being the visual sensation of what we see. For example, it is the patterns and contrasts of luminance that enable us to see volume through highlights and shadows. And it is this facility that makes it possible to carry out fine work such as threading a needle. In recent years, this has led to the use of digital cameras with appropriate software being used to convert the pictorial data into luminance information. However, this can only be possible if the values are converted to take account of the Vλ SPD. A camera’s spectral photonic distribution, though it can be adjusted, is usually similar to natural daylight. This is overcome by the use of a supplementary Vλ filter.

The pilot experiment involved taking a range of coloured items (socks) from across the colour spectrum and photographing them under daylight and comparing the image with a photograph of the same set-up but with the Vλ filter applied (see Fig 3).

The equipment was supplied by the Faculty of Electrical Engineering and Communication, the Technical University of Brno. The comparison shows clearly that colours in the centre of the visual range, the yellow and orange colours, appear very similar, but the ends of the spectral range, the reds and blues, are downgraded, as are their luminances when the Vλ filter is applied – but by how much?

To compare the luminance or reflectance of the different colours was considered but to use a standard instrument that would have an inbuilt Vλ filter would introduce a further problem.

This obstacle was overcome by converting the images into black and white and measuring the luminance of each of the samples. The results are shown in Table 1. Note that a correction of the values for the Vλ measurements had to be made because the daylight illuminance was not the same for both photographs. A comparison of the luminance values shows that the ratio between the values for different colours varies from 1.42 for yellow to 2.38 for blue depending on the individual colour.

This means that using the Vλ approach distorts the measurement of a lamp’s SPD and would affect the lamp

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Fig 3: photographs of the arrangements of coloured samples (socks). The top image is taken under daylight. The second image is also in daylight conditions but with Vλ filter

Fig 4: photograph of the array of colour samples labelled.

The measurements were carried out by averaging the luminance over a small patch on each sample

Lighting metrics

Column

W

X

Y

Z

Daylight

V(λ)

V(λ)x0.82

Daylight/ Vλ x 0.82

A

586

350

287

2.04

B

1919

983

806

2.38

C

1975

1106

907

2.18

D

2156

1853

1519

1.42

E

2356

2028

1663

1.42

F

596

506

415

1.44

G

875

470

385

2.27

H

496

277

227

2.18

I

1078

844

692

1.56

J

2422

1461

1782

2.02

Total

14459

9878

8099

18.92

Average

1446

9880

810

1.89

Table 1: Column W shows the luminance values for samples A-J with daylight illumination. Column X shows the luminance values for daylight illumination together with the Vλ filter. Column Y shows the luminance values of Vλ multiplied by 0.82 to correct for the differences in illuminance. Column Z shows the ratios between data from columns W and Y

efficacy. In addition, depending on the colour performance measurement approach, it can affect the colour appearance and colour rendering classification.

Where next?

Clearly this pilot experiment has limitations and the issue needs much more consideration. We need to have a better understanding of the colour response of human sight to enable electric light sources to be developed that provide the quality of colour performance, both colour rendering and colour appearance, on the basis of accurate measurement values.

Fig 5: the daylight spectral distribution together with a shape (black line) suggested as the area covering the human visual colour range (400-700nm) and an approximate daylight distribution (DVλ) suggested for light and lighting metrology

Recently Mark Rea of the Lighting Research Center at the Rensselaer Polytechnic Institute has suggested a Uλ SPD which embraces all the SPDs for the known vision receptors contained within the human eye. Perhaps a better solution would be to use a ‘smoothed’ daylight envelope covering the human spectral range 400-700 nm (see Fig 5). It covers all of the human visual spectral range, not equally, but very similar to daylight. After all it is common practice for people to use natural daylight when trying to assess colour samples or colour matches.

Then a light source SPD could be compared against the idealised vision/daylight measurement distribution described above. Perhaps labelled VDλ (V for vision and D for daylight)?

The comparison would need to provide for both colour rendering and colour appearance. To aid this process dividing the spectral range into bands as shown in Fig 6 may help.

This would ensure that each part or the spectral range is considered but would also take into account the overall shape by the amounts of radiation in each band.

A further consideration is not just the development of good colour rendering and colour appearance light sources, but light sources that might enhance human physical performance and any subconscious effects that might require light that is high in energy at the low wavelength end of the spectrum by activating the human body clock.

Or light at the high wavelength end of the spectrum that might enhance sleep and relaxation?

Modern light source possibilities that use combinations of LEDs or new fluorescent discharge lamps or even incandescent tungsten, or graphene lamps are possible, and lamp manufacturers need good standards by which to work.

In summary, this report questions the use of the Vλ SPD as the basis of illumination metrology, as well as the colour performance and efficacy of a light source. The basis was a pilot experiment of a limited scope but hopefully it will encourage the standards authorities and others to look again at the validity of the Vλ SPD. Acknowledgements: thanks go to Peter Raynham and the UCL team for help with the pilot experiment, and my son Dominic Loe for his help in carrying out the photo manipulation and some of the diagrams

Fig 6: the area for an approximate daylight SPD and human visual range divided into six equal wavelength steps, potentially for comparison purposes with a lamp’s SPD perhaps as a basis for colour rendering and light colour appearance.

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Lighting guidance

Work on commission With rapidly evolving technology outpacing the original CIBSE/SLL Commissioning Code L, a new extensively revised and rewritten 2018 version has just been published to address the latest developments The latest edition of Commissioning Code L, published

by CIBSE and the Society of Light and Lighting, has been extensively revised and rewritten to address the latest developments in lighting technologies and controls. The original version was first published in 2003 when traditional sources still predominated and the use of lighting control systems was less widespread.

Still based on the same principles, the 2018 update provides guidance on how to set up a commissioning plan for a project to ensure that the design intent is realised at project completion.

It also aims to ensure that users are fully aware of the operation and benefits of their particular lighting installation.

‘Commissioning Code L has been extensively rewritten because lighting installations are becoming increasingly complex, due to new technologies such as LED-based luminaires, advances in lighting controls technology and the now commonplace integration of luminaires, emergency lighting and lighting controls to form the lighting installation,’ explains author Sophie Parry. ‘Given this background of technological advancement, there is an increased risk of the lighting not being installed as designed and specified, which means that the completed installation may not operate according to the design intent.’

Equally applicable to new-build and to refurbishment/ retrofit schemes, the document advises on the stages, activities and actions required to commission lighting installations, and describes a process that aligns with the RIBA project stages of design, construct, completion and post-completion evaluation.

Covering the commissioning of interior and some exterior lighting systems, it is intended not only as a guide to good practice for commissioning but also to help define both commissioning and handover procedures.

It makes provision for any post-handover verification of actual lighting energy consumption to ensure that the lighting installation Commissioning Code L: equals, or ideally betters, produced to ensure lighting the energy-modelling lives up to design aims

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‘There is an increased risk of the lighting design not being installed as designed and specified, which means that the completed installation may not operate according to the design intent’ predictions during the design phase. Post-handover checks and modifications may also be needed as part of seasonal adjustments, ensuring that the lighting installation continues to operate at optimum performance as the seasons and available natural light levels change.

‘The code emphasises the importance of providing the customer with accurate operating and maintenance information, which may now exist as a building information management software model, rather than as traditional paper-based documentation,’ says Parry. ‘Without accurate O&M information, it will be increasingly more difficult, and therefore costly, to maintain, fault-find or extend the lighting installation during its life cycle.’

Code L also emphasises the importance of providing the appropriate levels of training as the lighting installation nears completion. ‘This part of the commissioning process is important because the facilities managers will be tasked with ensuring the lighting installation operates to agreed service levels and the actual users of the building will need to understand how the lighting works and its benefits,’ says Parry.

‘End-users may experience automatic changes in artificial light levels and colour in their working space, but may not understand the reasons,’ she continues. ‘There may also be manually operated lighting scene controls that end users can use for their benefit, but usually only if they are shown how to use them as part of their training.’

For further information, or to purchase a copy of Commissioning Code L, go to www.cibse.org/knowledge

LR&T essentials

Body clock watching Iain Carlile finds that the effects of light on the circadian system figure in the latest LR&T online papers

Nagare et al’s paper explores a topic that has been in the popular media for the past few years, and that is what impact the use of self-luminous displays (such as tablets and smartphones) before bedtime can have on a person’s sleep. In their paper they investigate whether the Apple Inc mobile device Night Shift application is effective in reducing melatonin suppression, a marker of circadian phase.

An experiment was conducted in which the subjects experienced four different conditions: a dim light control, a high circadian stimulus true positive intervention and two Night Shift interventions delivering low and high correlated colour temperature light from the mobile devices. From the results of the experiment it was found that melatonin suppression did not significantly differ between the two Night Shift interventions, suggesting that changing the spectral composition of the mobile device display, without changing the brightness setting, may not be sufficient for preventing impacts on melatonin suppression.

Also considering the effect of light on circadian patterns, Figueiro et al’s paper investigates circadian-effective light in an office environment. A field study was undertaken in two US federal government offices and two US embassies. The study looked at whether the introduction of circadian-effective lighting (with circadian stimulus [CS] values of CS>=3) could be installed in order to reduce sleepiness and increase alertness, vitality and energy in office workers during the hours of work.

Circadian-effective lighting was introduced for a two-day period. A daysimeter device was used to measure participants’ CS values during both the baseline and intervention days.

Participants completed questionnaires on sleep habits, stress and feelings of vitality and energy. Comparing the intervention days against the baseline, results from the investigation showed that participants were exposed to significantly higher levels of circadian-effective light during the intervention days. From the questionnaire, self-reported sleepiness scores were significantly lower on the intervention days; participants also reported feeling more vital, energetic and alert. From the results of the experiment the authors conclude that a CS>=3 can reduce sleepiness and increase vitality and alertness in office workers.

Tang and Teunissen investigated the differences between Dutch and Chinese subjects in their preference for the LED

white light source used for the illumination of fresh food, packaging material and skin tone. Participants were asked to assess the attractiveness of the object’s appearance for seven different light sources at two CCT settings, 3000K (Dutch and Chinese subjects) and 4000K (Chinese subjects only), and a range of different colour rendering indices (Ra) and colour gamut (Ga) values.

Generally both Chinese and Dutch subjects preferred light settings with an increased colour gamut for the illumination of fresh food and packaging material, although differences were found between cultures for the preference of colour rendering indices with a strong red colour saturation. When assessing the attractiveness of skin tone, the Chinese sample did not like an increase in red saturation at 3000K but did not mind the same increase at 4000K. There was no clear relation between skin tone preference in the Dutch sample. The authors conclude that object attractiveness is application-dependent, gender-specific, culturally related, and influenced by the CCT of the light source.

Iain Carlile, MSLL, is an associate of DPA 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) The appreciation of LED-based white light sources

by Dutch and Chinese people in three application areas X Tang, C Teunissen Does the iPad Night Shift mode reduce melatonin suppression? R Nagare, B Plitnick, MG Figueiro Circadian-effective light and its impact on alertness in office workers MG Figueiro, M Kalsher, BC Steverson, J Heerwagen, K Kampschroer, MS Rea

Top left: desktop luminaires used in a study of circadian-effective light in an office environment (Figueiro et al)

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2018 12 March Junior Ready Steady Light (SLL event) Venue: Rose Bruford College, Sidcup sll@cibse.org 13 March Ready Steady Light Venue: Rose Bruford College, Sidcup sll@cibse.org

20 March CIBSE Scotland Conference Speakers include: Chris Stark, director of Energy and Climate Change at Scottish Government Venue: Technology Innovation Centre, University of Strathclyde, Glasgow www.cibse.org/networks/regions/scotland 21 March WELL and Daylight; CBDM and Health (organised by CIBSE Daylight Group) Speakers: Dr Cosmin Ticleanu, principal consultant: Lighting, Fire and Building Technology Group, BRE, and Andrew Bissell, director of Light4, Cundall Venue: National Gallery, London WC2 sll@cibse.org 12-13 April CIBSE Technical Symposium: Stretching the Envelope Venue: London Southbank University www.cibse.org 25 April How to be Brilliant (organised by the ILP) Speaker: Sally Storey, director of Lighting Design International Venue: Body and Soul, London EC1 jess@theilp.org.uk 26 April SLL Lighting Knowledge Series: LightBytes Venue: Life Meetings and Events, Newcastle-upon-Tyne sll@cibse.org 2 May Electrical know-how for architectural lighting designers (organised by the ILP) Venue: Conway Hall, London WC1 jo@theilp.org.uk 8-10 May Lightfair Exhibition and Conference Venue: McCormick Place, Chicago www.lightfair.com

Arup site, RSL 2017

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13 March: Ready Steady Light, Rose Bruford College, Sidcup

10 May SLL Lighting Knowledge Series: LightBytes Venue: Fifteen Ninety Nine, Glasgow sll@cibse.org

Lighting Knowledge Series: LightBytes The Lighting Knowledge Series is kindly sponsored by Fagerhult, Trilux, Xicato and Zumtobel. For venues and booking details: www.sll.org.uk

10 May WELL Building Standard (organised by SLL and CIBSE Scotland) Speaker: Helen Loomes Venue: Teacher Building, Glasgow sll@cibse.org 16 May LR&T Symposium (and International Day of Light) Venue: Darwin Building, UCL, London www.lightday.org www.sll.org.uk 23 May How to be Brilliant (organised by the ILP) Speaker: Lisa Hammond, director, Gravity Design Associates Venue: Body and Soul, London EC1 jess@theilp.org.uk 7 June SLL Lighting Knowledge Series: LightBytes Venue: Barbican Centre, London EC2 sll@cibse.org 17-22 June 16th International Symposium on the Science and Technology of Lighting Venue: University of Sheffield www.is16.org 27-28 June Smart City Event Venue: Zuiderstrandtheater The Hague, Netherlands www.smart-circle.org/smartcity/

LET Diploma: advanced qualification by distance learning. Details from www.lightingeducationtrust.org or email LET@cibse.org CIBSE Training: various courses across the whole spectrum of lighting and at sites across the UK. Full details at www.cibse. org/training-events/cibse-cpd-training LIA courses: details from Sarah Lavell, 01952 290905, or email training@thelia.org.uk For up-to-date information follow us on Twitter @sll100