More ways to listen to the LED lighting journey
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Summary
In Episode 2 of Retrofitting Our Reality, Rebecca Stewart speaks with Florence Lam about the LED lighting journey and why it mattered: not just for lowering energy, but for better buildings and infastructure. From Millennium Bridge to Leicester Square Gardens and Arup’s 80 Charlotte Street, Florence shows how lighting shapes behaviour, confidence and connection in public space, and what it really takes for an innovation to move from “new” to everyday default.
In this illuminating episode, engineering demonstrates how projects have pushed the boundaries of lighting design to deliver safe, connected, and socially impactful experiences for the people who use them.
The LED lighting journey: key themes
Key themes at a glance:
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The LED lighting journey | From innovation to mass adoption, and what made it stick
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Lighting as social infrastructure | How public spaces feel after dark, and why confidence matters
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Beyond the brief | Trust, collaboration and taking people with you, step by step
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Comfort and circadian rhythm | Why static lighting assumptions often fall short in real life
Using projects like the Millennium Bridge and Tate Modern, Florence Lam brings it back to a better starting point: stop beginning with “how bright?”, and start with how a place should feel. In the public realm, lighting isn’t only about visibility. It influences behaviour, wellbeing and whether people choose to move through a space, stay in it, or avoid it altogether.
The episode also follows the LED journey from early use to everyday default. The retrofit lesson is simple: adoption accelerates when the benefits are obvious in daily life, and when delivery and operation are realistic for the teams who have to live with it.
Florence returns to one discipline throughout: ask better questions before you reach for new tech. “If technology is the solution, what was the question?” A reminder that human-centred design starts with purpose, not specs, and that the best outcomes are often the ones you feel before you can explain them.
“You can’t just look at numbers on a page… you have to understand the why.”
Florence Lam
Arup Fellow and global lighting design leader
Mentioned in the LED lighting journey episode:
Places + projects
Organisations
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Arup
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Artus Air
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City of London (client body referenced)
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Southwark (client body referenced)
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Philips (lighting manufacturer referenced)
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Citizen (LED manufacturer referenced)
Lighting + technology
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LED lighting (including early “blue LED”)
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Media façades / “architainment”
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Luminaires
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Light pipe / “blade of light” concept
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Polycarbonate pipe (light pipe explanation implied)
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Optics: lenses, collimators, parabolic reflectors
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Controls (optical + colour control)
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Fluorescent lighting
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Colour temperature examples: 3000K, 4000K, 17,000K
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IoT spectrometer (capturing daylight data)
Human factors + design concepts
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Human-centred design (designing for users, not just the client)
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Psychological safety (confidence at night; “reading faces at a distance”)
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Circadian rhythm / melatonin
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Evidence-led design (pre- and post- checks; “go back and see what changed”)
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Incremental vs disruptive innovation
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Cost vs value (“don’t talk about cost, talk about value”)
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Public realm regeneration / night-time economy
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Neurodiversity and personalising environments
Transcript
*Transcript edited lightly for clarity while preserving the original meaning and tone.
[00:00:00.000] Rebecca Stewart
Welcome to Retrofitting Our Reality, a podcast brought to you by Artus Air.
I’m Rebecca Stewart, CEO and Co-Founder of Artus Air, and it’s my pleasure today to welcome a guest who has seen how technology can disrupt an industry, not only for efficiency, but for the opportunity it presents in how we light up our lives.
We’re recording today in Hilson Moran’s award-winning workspace, The Living Lab, a home for innovation, collaboration, and a test bed for the “new” in our industry.
Florence, I’m hugely honoured to have you here today.
[00:00:39.000] Rebecca Stewart
You were a big inspiration to me early in my career in the built environment, carving out space for lighting design from a very traditional electrical engineering discipline, and doing that while raising a young family. Thank you for taking the time to join us. Please introduce yourself to our listeners.
[00:00:59.000] Florence Lam
Thank you, Rebecca, and I’m honoured to be invited to have this chat with you.
I’ve retired from a company called Arup, where I worked for over 35 years, even before I graduated. I started as an electrical engineer, and my expertise is in lighting design.
Before I retired, I was also a Regional Board Director, overseeing Arup University and our Ventures operations as well.
[00:01:29.000] Rebecca Stewart
Fantastic. Can you bring a couple of projects to life that listeners might have heard about?
[00:01:42.000] Florence Lam
Yes, absolutely. But before I do, I want to mention lighting design at Arup.
Lighting design evolved as a specialist discipline, and I was also one of the co-founders of the lighting practice within Arup. Over the years, we evolved from four people based in London to globally more than 120–140 lighting designers across different continents and offices.
Thinking about projects, the memorable ones are often closely aligned to my life stage. When I was pregnant with my first, I was working on the Tate Modern project, converting an old power station into a modern art museum. So that’s repurposing, really, right from then. I can come back to that later.
And the second one was the Millennium Bridge. When I was designing it, I was pregnant with my second child. That was another very memorable project, because it was a new bridge across the River Thames, the first new bridge for over 100 years.
That was also a time when I took lighting in a different way. Not just looking at standards, how do you light a bridge to whatever lux levels on the horizontal plane. But actually asking: if you have a new bridge crossing the river at night, in the middle of London when both banks are buzzing, how do you want people to actually feel when they’re crossing that river at nighttime? What’s the opportunity that lighting could bring differently on that bridge?
[00:03:35.000] Rebecca Stewart
If we think about design thinking, what gave you the opportunity to think like that? Because you need space to be able to have those thoughts.
[00:03:47.000] Florence Lam
I think it’s in me that I always question what I want to do and what I want to be.
I studied engineering at Cambridge, but while I was doing that course I found there was something missing. The course was very technological, numerical, a lot of mathematics. But what’s the purpose of learning engineering? What is missing?
That’s the point where it dawned on me that lighting is a very interesting subject, because it’s not just the physics part of light, and it’s not just the engineering part, the technology of providing enough lumens on the surface for people to see.
There is something in me that, when I enjoy a show in a theatre or a musical, the light stirs something. And when I was doing student productions at university, that’s what I tried out and played with. There was something more than a number, and that’s what I wanted to explore.
So whatever projects came my way, I always questioned: what else beyond the number can add to a finer outcome?
[00:05:04.000] Florence Lam
At the time, when I wanted to do lighting design, all the legends I saw in the industry were brilliant, but they didn’t come from engineering. Sometimes when I read journals and magazines about lighting projects, there was an undertone that anyone from a technical engineering background cannot design.
That became a challenge. I thought: really? Is that how we approach it? I have the baggage of being an engineer, but I’m sure I can do better than that.
Engineering wasn’t linked with design at all. In my head, engineering is a very technical, brilliant toolkit. But I couldn’t take that directly into the field I really wanted, because the people I saw doing great work came from design backgrounds, architecture, etc. It almost precluded me from joining that community.
[00:06:19.000] Rebecca Stewart
Do you think the split was defined as a creative designer rather than an engineer with a toolkit, and therefore more in touch with the human aspect and the “why”, the feeling we’re trying to create? Do you think at the time that was the association of design rather than engineering?
[00:06:43.000] Florence Lam
Yes. It came across like a “black art”, something very intuitive.
But being nurtured in the Arup environment, I also learned that whatever we do as an engineer to arrive at a good solution is actually a creative act. We just never defined it like that. Society doesn’t define “creative” as someone who could come from a technical background.
In Arup, the philosophy is that creativity brings a lot more things together. There’s an art element, but more critical is being relevant and socially useful to society. Good outcome. And what does “good” look like? Because good doesn’t just look like you can see where you’re walking across the bridge.
Innovations, when we talk about innovations now, creativity definitely is an element that needs to be there. And it doesn’t just mean beautification or style, superficially what things look like. What it really means is: has that journey been a good feeling, and has it supported you going from A to B?
[00:08:30.000] Rebecca Stewart
Staying on the Millennium Bridge for a minute, because there were so many other parties involved, not just Arup. What was it about the other parties, the clients, the people building the bridge, the City of London, councils, whoever, that came together to allow you to push that agenda? That we need to think about the people crossing the bridge.
[00:08:55.000] Florence Lam
That’s a very interesting point, because it got me to think: what does the bridge actually symbolise? It’s about connection.
So it’s no point of just one person dreaming “what if”. It’s asking: how about doing lighting differently, and how do you actually convince people to come on that exploration journey with you?
There was the architect, and at the time there was a lighting approach they used a lot. But the concept for that bridge was “blade of light”. You draw a line on a napkin, instantly you’re connected into the whole architectural philosophy. Lighting was in the name of the concept.
So there’s a blade of light, but how does that relate to people and make it meaningful for them to cross that bridge?
I visualised that if I were to cross that bridge in the middle of the night, lighting cannot be distracting. It’s not just about lighting the face. It’s lighting the bridge. It needs elegance. It needs to create safety so you won’t fall off, but also psychological safety.
If I’m walking alone along the bridge, I need to have enough light on faces, not just my face, but someone else approaching at a distance, enough that I can decide: do I turn the other way, run, or keep going? I’m not anxious about it.
So it’s how you create that element, bring others along, and make it meaningful.
[00:10:37.000] Florence Lam
Sometimes it’s not just talking, it’s demonstrating. Go down to other bridges along the river. What do people see? What brightness is sufficient? People remember a bridge feels good or not, but it’s not a number. Sometimes they’re surprised that the numbers don’t correlate to what they think is the right environment.
You can’t just look at numbers on a page. You actually have to tread the path and feel it for yourself.
[00:13:06.000] Florence Lam
One thing I’ve learned is: don’t just leap as if everybody’s got it at the end.
I’ve learned over the years that I need to take mini steps and bring people with you, because you could be exploring. I was exploring as well. I didn’t know the final result would work perfectly. I could imagine, because of professional knowledge and experience trying certain things, it could work. But others don’t have the same expertise. They do have experience of running cities. What works at night, what doesn’t. They know there are other essentials that need to come in.
So what I bring to the table is different from what they bring to the table. It’s equal. You respect each other’s expertise, because they’re entirely different to your own. Together they bring value, and they bring insights that verify whether the scheme works.
You also have to respect that they have the remit to maintain the bridge. It’s not something you finish and walk away. Bringing those people in right at the beginning creates ownership. They’re carrying the baby for decades to come.
[00:15:22.000] Florence Lam
The bridge structural design was done in eight-metre modules. So with a light pipe, it was done as eight metres. You’ve got a light engine at one end of a pipe, and you pipe the light along a tube.
Think about water. You push water along a tube. That’s the idea.
[00:15:53.000] Florence Lam
The bridge design was around 1998. LEDs were around, but before mass commercial adoption. You could see it coming, but it didn’t have the power.
At the time, it was adopted more in entertainment, which evolved into “architainment”, media façades. That was one of the first mass adoptions of LEDs.
For mainstream architectural lighting, white LED efficiency had to become comparable to fluorescent. For bridges you need higher power, and it didn’t have that power. And to get that power you needed big LED chips, so optics to focus those big light sources into precise angles was hard. With LED you need collimators or lenses to refocus light, but because the source is large it’s harder to get precision.
[00:18:00.000] Florence Lam
When we talk incremental innovations, manufacturers do R&D and we adopt the product when it’s better than the old one.
But with disruptive innovations, LEDs suddenly could match or beat traditional light sources. At lab level, you could get a lot of light out from little power in, in small batches. But now you need to control the light. The way you control it is different from traditional sources because the form factor is different. The whole industry has to learn something quite different.
Manufacturers also had to be cautious because there’s big investment. Which way do they put their money? They want to be early, but they don’t want to get it wrong.
There are really good manufacturers that reach out to designers and ask: what do designers really want with LEDs? It’s not just the power, not just energy efficiency. It needs to be appropriate for the solution we’re designing.
[00:20:22.000] Florence Lam
Manufacturers at the OEM level, and luminaire manufacturers too, did this. Citizen was one example. They took designers to see their latest LED technology in their lab.
Not just power, because you can make it as bright as you want, but controls beyond optical controls, colour controls, things you can now do that you could never have dreamt of as a designer.
I love this because it’s iterative. You can’t always think of the impossible. Sometimes designers have imagined solutions but there was no technology to make it feasible. Sometimes you’ve never dreamt before, but suddenly you realise you can do that with light, and you had that opportunity before.
If you take the two together, where else can you take that opportunity?
[00:22:41.000] Florence Lam
Every project, if you seek harder, there could be new opportunity to do things slightly differently and get a better solution. That builds your confidence, but it’s not about being the expert who knows the answer. It’s more that because you’re the expert, you have more questions to ask. You know what you don’t know.
And there’s always this quote close to my heart: if technology is the solution, what was the question?
Why do you want to use the technology? Is it just energy efficiency? We know it has to tick that box. Is it low carbon, now zero carbon? This is understood. But if we’re moving into a new innovation, someone is going to invest money in it. How do you max out the value? It has to go beyond energy efficiency and low carbon. It has to be something really meaningful to people that past technology doesn’t solve or give you that advantage.
[00:24:14.000] Florence Lam
The “five whys” doesn’t have to be five, it could be three, but asking why is so important.
It’s easy to describe to a client what the concept is. How you convince them, meet cost and time, feasibility and viability, that’s also doable. But in the end, if it’s not desirable, if it’s not meaningful to people, if it’s not serving the people, place, or purpose, it’s useless.
There have been many examples in office buildings where a developer does the fit-out, tenants come in, and all the lights go to the bin. You can tick boxes, but if it’s not right for whoever is moving in, it’s not going to be used, and it’s worse for carbon.
So it’s the design phase and being conscious about why you’re doing that.
Design thinking is human-centred. You need deep understanding of users’ needs. People say “be in the client’s shoes”, but actually be in the users’ shoes. That’s a lot more important, because then we have a common goal.
It’s more than cost, more than comfort or carbon. It is the context of who you’re designing for. Why? What are they doing with that space? Why would certain people be more productive, in whatever terms you define productivity? Productive might mean more creative, more collaborative, more inspirational. Productive isn’t just stamping papers.
Different needs to get people to work in a space.
[00:27:18.000] Florence Lam
Work has evolved. You don’t just sit in front of computers and type. There’s a lot of social interaction. You want to encourage collaboration, but also give people choices.
Lighting can give people subtle cues. This kind of lighting helps you think deeper, focus, concentrate. This kind of lighting, if you’re in that zone, subtly signals “I’m focusing, don’t talk to me.”
Daylight is great, but some people can’t work with too much daylight. We need to respect spectrum of preferences, including neurodiverse people. Variety and giving people choice, the ability to personalise their environment, is important.
[00:28:34.000] Florence Lam
Daylight is the best light. Light is fundamental to our social infrastructure: how we interact, how we live daily life, work, at home, at play. It’s the whole thing.
It’s not just about seeing physical elements. It’s also the physiological aspect. Research into light and our relationship with light tunes our body, circadian rhythm. It also influences psychological effect: do I feel good, happy, sad, tired, alert?
When you don’t have daylight, especially in winter, three or four o’clock is still a work time. So how do you work with that flow?
Technology exists and gives you opportunity, but you need to explore and you have more in your toolkit. That also means you have the opportunity not to design a space that’s static. You can design something like a living lab.
[00:30:25.000] Florence Lam
At Charlotte Street we made it a living lab because we give people control, and we can test in real time. How do we learn better with real people? Next season, next year, it can be better.
We installed an IoT spectrometer on the roof to capture how daylight varies across seasons, time of day, intensity, weather. Blue sky has a different spectrum to an overcast sky. So you bring the outside in, rather than prescribing what you think might work and walking away.
Syncing with daylight is good, because we don’t want to play god. We are lighting designers, not chronobiologists. We need to be careful what we prescribe, because light dosage is important to people, not just plants.
[00:33:11.000] Florence Lam
Before LEDs, there were fluorescent lamps with a high blue content aimed at synchronising circadian rhythm. We tested different lamps and combinations over weeks, swapping between 3000K, 4000K, 17,000K, uplight and downlight, to mimic the sky.
What we didn’t realise is there was a moment when we had everything at 17,000K all the time. People stayed late, and their melatonin was suppressed so much they couldn’t sleep at night.
So we learned it’s important that, even with lighting, we have responsibility to understand the science and long-term effect. Research can only be narrow; you need to ask why. You need to experience and test before prescribing to clients.
[00:36:12.000] Florence Lam
As LEDs became more mainstream, and because of climate change, cities pledged to replace street lighting with LEDs. That’s a huge investment and a rare opportunity to change lighting infrastructure in a big way.
It’s an opportunity to explore lighting doing more than lighting a street: public realm regeneration, the night-time economy, getting people confidence to go out, meet each other, sit on a bench in a park.
Leicester Square Gardens was one example. There were issues around crime, and the city needed to close the garden after certain hours. The garden became a place people walked around, not somewhere they stayed.
So we learned about the garden and people’s behaviour, and we gathered evidence. We did people counting, mapped footfall, day and night. Destinations matter, but it was interesting that people weren’t staying in the garden.
When we redesigned the lighting, we asked: how do we use light to enhance the space, nudge people to behave differently, and to dwell?
Because dwelling helps people feel safe. It’s not the amount of light. It’s creating an environment people dwell in, where they can meet, sit, be seen, feel safe.
But it starts with evidence and asking why. And when you complete it, you go back. Don’t assume anything. You do post-occupancy survey to check if it helped.
You ask the question beyond the brief. Ask the why. If you don’t understand why, get evidence. Is it real or just perception?
[00:40:06.000] Rebecca Stewart
If you could give one example of a hurdle in the LED adoption journey, what would that be?
[00:40:13.000] Florence Lam
There’s always the cost, but the way to overcome it is you don’t talk about cost, you talk about value.
[00:40:18.000] Rebecca Stewart
If you were to put the future of our industry in one word, what would that word be?
[00:40:26.000] Florence Lam
Empowerment would be my word. Everyone needs to feel empowered that they can do change, and that’s by showing examples like this podcast, like you, that change can happen.
[00:40:39.000] Rebecca Stewart
Brilliant. My one word is enlightenment.
It has multiple meanings related to light, but more important is knowledge sharing and being open. You need to learn, but also help share knowledge. It’s not about “educating”, it’s bringing people along on that journey, and then we get enlightened together.
[00:41:10.000] Rebecca Stewart
One last question: what would your family say if I asked them what you do?
[00:41:15.000] Florence Lam
I think the way they’ve seen me talking about light, they don’t believe I go to work every day. They just think I’m having fun every day.
[00:41:28.000] Rebecca Stewart
That’s wonderful. We should all be in our jobs.
Florence, thank you so much for coming along today. I really appreciate it. We’ve talked for a long time without a break, which is amazing. I think it’s going to give our listeners understanding as they go through their journeys and experience spaces at night: why they feel anxious or safe or cosy, and what’s giving them that feeling.
Thank you, and thank you to our listeners. Thanks for tuning in, and please do come back and listen again at our next podcast from Retrofitting Our Reality.
[00:42:05.000] End