Designing for: Lighting and the Circadian System (Season 1, Episode 4)

Inclusive Designers Podcast
Inclusive Designers Podcast
Designing for: Lighting and the Circadian System (Season 1, Episode 4)
  • Edited by: Andrew Parrella
  • Guest: Catherine Leskowat

Catherine Leskowat discusses lighting and the circadian system and how important it is for our health and wellbeing. In this episode, topics will include: Aging, lighting, acoustics, preventing falling, lighting design for showrooms, blue vs. red light, and our circadian system.

Catherine Leskowat is a lighting designer with Lam Partners of Cambridge, MA, where she also serves as chair of the Science Lab. Catherine currently teaches lighting design for architecture at the Boston Architectural College, and co-leads a Boston women’s-interest networking and thought-leadership group, BOSLady. Catherine has been active in the IALD (International Association of Lighting Designers) since before graduating from the University of Oklahoma in 2013 with a bachelors in Interior Design, and serves on the IES (Illuminating Engineering Society) Progress Report Committee.

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Additional Reading:


Illuminating Design: Lighting Design & the Circadian System
Guest: Catherine Leskowat


Janet: In this series we will be discussing specific examples of design techniques that can make a positive difference for people living with certain human conditions.

Carolyn: The more a designer understands the client and or the community the more effective and respectful the design will be.

(Music up, then lower)

Carolyn: More and more studies are showing how better sleep cycles can aid in recovery and disruptive patterns can lead to long term health issues.

Janet: We recently had an opportunity to sit down with Catherine Leskowat to understand the connection between circadian cycles, health and lighting design.

Carolyn: Before we get into that discussion let me tell you a little bit about Catherine and her qualifications: Catherine Leskowat is a lighting designer with Lam Partners in Cambridge Massachusetts where she also serves as chair of the science lab. She currently teaches lighting design for architecture at the Boston Architectural College, or BAC. Catherine has been active in the International Association of Lighting Designers since before graduating from the University of Oklahoma in 2013 with a Bachelors in Interior Design. And she serves on the illuminating engineering society’s progress report committee.

Janet: In today’s discussion. We explore the impact that circadian cycles have on our health, and how lighting design and materials can be used to improve it.

(Music- transition to Interview)

Janet: Welcome to Inclusive Designers podcast. My guest today, Catherine Leskowat.

Catherine: Yes.

Janet: Yes… I pronounced that correctly. I’m very excited.

Catherine: You can introduce me any day.

Janet: Thank you Catherine for coming today and participating in Inclusive Designers podcast.

Catherine: my pleasure.

Janet: Start off this program today and tell us just a little bit about yourself and how you got into lighting.

Catherine: Sure, OK. I am an architectural lighting designer here in Cambridge Massachusetts. I would say for anyone interested in lighting, the bug is going to bite you so fast. I think that lighting is for people who love design, and I actually studied interior design just to get into lighting. My favorite people in the world are architects and interior designers they inspire me so much and so, I wanted to do something that showed off their work and kind of completed the puzzle.

Janet: I did not realize that, that’s actually really terrific. So, Catherine, you work at Lam Partners in Cambridge Massachusetts just across the Charles from here. Can you tell me a little bit about like, what is it that you actually do and how you go about your day?

Catherine: you want to hear the elevator pitch…

Janet: That would be great.

Catherine: I love hearing this question from everyone because lighting design is still a pretty niche field and most people don’t have any idea what a lighting designer would do. And I think about how light affects your perception of space, how it affects your performance at a task, and even your wellness overall. And I work from concept through to specification and reviewing of the site after everything has been installed and is hopefully working. I am a consultant to architects. I work really closely with electrical engineers, contractors, architects, interior designers.

Janet: Right, that’s interesting, because you don’t work in a vacuum (no, no), do you know what I mean, you always work with other architects and other planners…

Catherine: Well, that’s what the name of your podcasts says to me. I’m not sure if that is exactly what you meant it to communicate but that’s what it says to me is you’re thinking about involving all the voices in design and really getting those collaborators to work together on a much more fundamental basis than we normally do.

Janet: Thank you for getting that.

Catherine: Okay, good. I wasn’t quite sure but…

Janet: Right, Inclusive Designers has a sort of a double entendre because it’s not, I mean, it is about inclusivity, but it’s really also about inclusivity with other designers and sharing the information (yes). Right, and for you in particular, I mean, no matter where you go, you got to have some sort of light. Like you said, you got to go and illuminate the work that the designers do.

Catherine: Yes, so, I have my dream job. I get to work with really smart and creative big picture thinkers that make things every day that affect people’s health and wellness and productivity and all good things.

Janet: So, one of the things why I’m having you here today is we want to talk about health and wellness in terms of lighting and design. And I think the way to start this particular program is to perhaps talk a little bit about the circadian system. Can you talk to our listeners a little bit about that, and what is it, and why is it so important?

Catherine: Sure, sure… I think it’s a bit of a leap from architectural lighting to health and wellness, so, we want to kind of step through that. We know that light is not just visual. So the light that let us see the red ball and the puppy and the green grass is doing one thing, but we also have another photo receptor in the back of our retina that’s catching light before it gets to the imaging center and it heads directly to the brain. And we’ve been researching that since about 2012. We got some really good data on the fact that light also entrains our brain to a 24-hour cycle, and…

Janet: And that’s the circadian system.

Catherine: Yes exactly. So, if we have proper light exposure then we keep our master clock as it were, like the atomic clock of our body, on time and running all the other rhythms of our body healthfully. And that in turn is connected to your mental health, your physical activity, it even down the road has been connected to your odds of getting cancer and a lot of other illnesses. So, it’s connected to your immune system and your mental health which is connected to everything.

Janet: Right.

Catherine: So, we’re, the right amount of light comes from the fact that without light we actually fall into a longer than 24-hour day. So, if you’re on the moon or in a submarine without access to the sun, then you’re going to fall out of sync. You’ll be, you’ll have a little bit longer day, you’ll start going to bed later and then having a really hard time waking up, need two cups of coffee, three cups of coffee instead of just one and that’ll keep exacerbating itself and lead to health problems. There is another factor that we have to be aware of in this equation. Not only are we interested in light health, but the light health in turn impacts our sleep quality. And it’s the sleep quality that really regulates our hormone levels and our immune system and in turn leads to all of those mental and physical wellness issues that we’re becoming more and more aware of.

Janet: But isn’t healthy lighting just really just better daylight exposure.

Catherine: I love that question. Absolutely, that’s a great question to consider as architects and interior designers and lighting designers and wellness designers of all trades. Daylight is the original healthy lighting. And I think that education of the users and access to daylighting is still my primary passion in solving for healthy lighting. So wherever possible, we absolutely want to use daylight and daily habits of your users to regulate a healthy circadian system. (J: Right.) Where that is not practical, say for your submarine dwellers or your (J: Moonwalkers) night shift workers. Exactly, exactly. Or in buildings that really don’t have enough access to daylight. We want to provide full spectrum lighting systems that are a little bit higher output than we’ve historically been using in order to provide a stimulus that is significant enough during your morning especially and early afternoon hours so your circadian morning even if that’s not the sunrise.

Janet: Why is that important? Why is it the morning and the early afternoon? What makes those two times of the day particularly special for this, the circadian system.

Catherine: It gets really nerdy because it has to do with supporting your melatonin production and secretion. So, you don’t want to suppress melatonin in the evening. We want to (J: promote it) withdraw light exposure, especially from in the blue spectrum so that melatonin can be produced and expressed in your body. But in the morning, we want to wake you up and suppress melatonin so that it’s saved for the evening as it were.

Janet: And that is the blue lighting we hear about right, that’s the. (C: Yes.) the color Blue is very important, whereas Amber is more important later in the evening… am I understanding that correctly?

Catherine: Sure. So, it is really hot around a particular… (J: or am I simplifying it). No, it’s a good way too for people to relate to it, for sure. I think the word blue can be a little bit deceiving because not all light that looks blue is scary and awful for you. Your indicator light on the alarm clock or the TV is probably not going to hurt you at all. So, we try to when we’re providing a circadian stimulus, we want to accent that part of the spectrum and then when we want to allow you to calm down at night and not have that stimulus, you draw out all of the blue together. And yes, we would want to stay in more the amber. So, the color that light looks isn’t always true to its spectrum, but most likely you’re brighter and your bluer sources are the ones we want to avoid. So, your night shift app on your iPhone or the Android equivalent is actually doing just that for you. It’s filtering out the high end of the spectrum and it is dimming down the light level, because both of those are factors, the intensity and the color.

So, the visible light spectrum kind of starts, well it starts at around 400 nanometers, which would be the color Violet. And just beyond that outside the visible spectrum is infrared light which we cannot see, and that’s the threshold there is this Violet that is actually really super engaging to look at because it’s right at the visible light spectrum. And then we max out at about 700 nanometers, and that is our reds. So in between, every color, every nuance of color, has its own— four hundred twenty, four hundred thirty, four hundred fifty— nanometer value along the visible light spectrum. (Hmm!) Yeah! So, I want to see a nice little graph that has a curve along every nanometer value. And hopefully that’s not up and down a lot with maybe a lot of this blue but none of that blue and a lot of the green and none of that green. But I want to see a pretty smooth curve. And for circadian stimulus I want to see it going up in the 490 range which is the non-visual response peaks there.

Janet: Now is that particularly in the morning, is that, because that would be, right, part of the circadian system, it would be more advantageous to have the bigger blues in the morning, and then the more of the ambers, you know, in the evening. (C: less of the blue.) less of the blue, right.

Catherine: Exactly, exactly.

Both: C: See, you’re a pro… J: you’re a good teacher. I appreciate you being here… C: I love it. I’ll do it all day long. J: Okay, that’d be great. C: I do in fact. (laughter).

Janet: Okay, making sure we understand, we’re going through this process together. Thank you, Catherine. Alright, so to kind of keep moving forward, so how do we make sure we’re applying light strategies and in a helpful way and not continuing to create health issues within the built environment. I mean I know that, you know, one of the projects that you and I worked on, they had a fan that would turn on if they were go into the bathroom in the middle of the night and it was this high fluorescent light. And we recognized that this was very problematic for people trying to go back to bed after having gone to the bathroom before they, or you know in the middle of the night. Because the blue light, right, you know, was turning on and that was stimulating their brain… is that correct?

Catherine: Sure. In that project we had two huge factors working against us, both the auditory cacophony, (J: Right), and the light exposure.

Janet: When they turned on the light the fan, the overhead fan went on as well. So, you know it was a double whammy.

Catherine: They’re awake for sure. (J: Right.) Yeah, I think that short answer is that, it’s more important that we do act, then that we should be afraid of misapplying these strategies. Anything, any work we do to put in place these principles that we’ve talked about, you know withdrawing the blue spectrum in the evenings, providing extra stimulus intensity and blue spectrum in this circadian morning, both of those things are going to improve our average users’ “entrainment” is the term that we use for healthy circadian system. (J: Right). So, if we can take small steps by boosting light levels and in some instances using a spectral tuning system that allows us to take the blue in and out of the same light source. And ultimately encouraging our users to gain a little understanding about their own circadian system and how they should manage that beyond their say office space exposure (J: right). All those things are just going to do good in the long run.

Janet: Can we as designers design for people in homes, in their homes or how can people just who are listening who might be interested in trying to help their own circadian system within their own home. Do you have any suggestions on that?

Catherine: Yeah. This is actually my passion. I think that this is the way we solve this problem is by teaching everyone how to do it for themselves.

Both (overlapping): (C: I focus on the workplace simply because…) (J: That’s your job.) (C: so much of our population spends… it is also my job…) (J: It is your job, but you’re right, but we spend more and more…) (C: so much time) (J: in the office.) (C: Yes exactly.)

Catherine: But each of us actually have a little bit different natural day… So, it’s important to know— am I having trouble waking up? am I having trouble going to sleep? am I getting enough sleep? what is that sleep like? and I think eventually that will be a part of our fitness trackers. I think our light exposure will become something we track as well. Because it’s not a quick fix, it’s something that actually improves your health with the longer history of healthy entrainment. (J: Right). So, for most of us, we lean on the longer day side and the easy healthy maintenance for us to do, is make sure we get a minimum of 20 minutes and better, two hours…

Janet: 20 minutes of blue?

Catherine: … Of daylight. That’s your easiest way to get it. (J: Okay). There are of course some desktop luminaires that you can also get that are actually for SAD, Seasonal Affective Disorder.

Janet: We also live in New England. But it’s overcast too… and that can be you know that can affect people’s moods and I think that that’s partially because it’s the lack of sun.

Catherine: There’s actually a cap for our sensitivity to light so there’s a point at which the intensity no longer matters. And that’s relatively low threshold when you think about daylight because daylight can get really intense. (J: intense too) yes, yes in the hundreds of thousands of foot candles for luminance. So even on a cloudy day, you’re still getting almost the maximum level that your photo sensitive, your circadian sensitive to. So, it has a more of a mental impact, I think, than it’s having a physiological impact, those rainy days. But, your two hours in the morning, or 20-minutes if that’s all you can handle, sometimes that’s a commute. If you’re commuting in your car to work then you’re, you’re facing the cloud canopy or the sky glow. And that’s a great delivery of the illuminance that you’re looking for. Or if you can walk to work that’s also an excellent way to get it. (J: right) Or meditate with your eyes open maybe. Fun fact, your eyes, your eyelids actually filter out the blue. Isn’t that amazing.

Janet: That is amazing. So, when you talk about 20-minutes, so you’re talking about direct sun exposure and if you can’t get it from actual activity from outside. Right. And you’re talking about luminaires that can be, I’ve seen them, you said for the SAD, the Seasonal Affective Disorder. And so that’s one component that we can do. What about, what about like, helping us to go to bed at night. What would you recommend for that?

Catherine: So your morning two hours or 20-minutes whatever you can get, is going to help you peak melatonin in the evening at the right time so that your sleepiness and melatonin are coming together for you to really be able to go to sleep when you need to. But the second thing that you have to watch out for is, your slowing down rituals. So, at two hours minimum before you go to bed— better three to four— enabling something like the nightshift app on your phone so that you’re not getting too much illuminates from that, and slowing down on some of your social and physical activities, even not eating too close to bedtime— all of these are ‘Zeitgebers’— they all influence our circadian system. It’s just that light is such a huge factor. (J: Right). That’s the one we can control. But it’s helpful to take all of these into account. So, you start withdrawing your light and you start, maybe, getting off of social media and maybe you don’t work out right before bed and all these things will help in addition to your morning exposure, for you to be at the perfect spot to fall asleep and stay asleep for a good chunk of time. Yeah.

Janet: So, can you talk also a little bit about what you as a lighting designer would do within the built environment of say, like an office. Like what can we do to promote healthy lighting within the offices. As you pointed out, I mean, we spend so much of our day there.

Catherine: Yeah, yeah… A lot of what we’re doing is actually utilizing daylighting and really seeking to educate our user population. So, encouraging habits like taking a break, going outside, having a common space with really great access to daylight. So we want to, with the electric lighting system, provide a base level of a full spectrum and relatively high illuminance without any glare—we want to still be careful with glare and contrast issues—but ultimately, I think that we solve these with getting people up out of their desks and outside for a little bit. And providing common spaces everybody’s going to go to where they’ll really get that boost of daylight.

Janet: The daylight that they need. So, Catherine, you told me just recently a little bit about a showcase room, or showcase store, right, that you did recently here in Boston with the company, Lam partners, which is the company you work for. Can you tell us a little bit about the project? How did it come to be and what were the design issues within the circadian lighting and the lighting of the actual showroom itself?

Catherine: Sure, sure. Yes, that was a fascinating challenge from a wellness and just ergonomic standpoint. An existing showroom here in Boston, had not renovated the lighting system in quite a while, so lots of daylighting, some contrast issues because of that daylighting where the architectural lighting was underwhelming and causing some spaces to feel dark in contrast and not the amount of flexibility that they really need in a showroom. We would go through, you know, an initial collaboration with the client and the whole design team and talk about what it means to pursue WELL and how much that involves lighting…

Janet: And for our listeners that don’t know, can you explain a little bit about WELL…

Catherine: Sure yes, thanks for asking… WELL is a benchmarking system kind of like LEED and used in, mostly in commercial architecture, focused on health and wellness as opposed to sustainability like LEED is. So, encompassing all three of those things but really putting the users’ comfort and health and wellness first.

Janet: And there’s a bunch of different markers on WELL, W-E-L-L, and facets, and one of them is definitely lighting.

Catherine: Yes, yes. lighting is actually a huge component of WELL so and it can be complicated to navigate as a designer trying to calculate all of those goals

Janet: and especially within an existing building…

Catherine: …where you don’t always have great documentation existing and all about those materials and finishes, the translucency of your glass, and the finishes in the space. Yeah, that was a lot of fun. There were, there are two regular occupants in the showroom and then the rest are visitors throughout the day. So, we had a unique challenge of kind of following these occupants as they stationed in different desks throughout this space. It being a furniture showroom. So, not just one fixed perspective had to be considered, all of the possible perspectives of those few regular users. So, we ended up going with a cooler color temperature than they had previously, that kind of worked with their daylight exposure much better and brightened up the whole space a little bit. So even though there were so few regular occupants, we had to consider all of the places that they might be in and calculate their circadian stimulus from all of those angles and always starting with daylighting and in that case, we could actually achieve everything we were after with daylighting.

Janet: Well, we’re going to do a little something a little different. We’re going to try to mix it up a little bit… we talk about having an Inclusive Designers podcast be a helpful resource for other designers to come up with their own designs, and one of the threads that seems to be kind of keep going through is that evidence-based design for designing is still kind of new and we’re still kind of working out those kinks. So, one last question. Is there enough research, speaking of which, to start implementing these solutions just yet?

Catherine: Yes, I believe there is, definitely to start. There is a lot of research. There’s a very interesting conversation recently in the lighting design community about whether that research meets all the levels of say, an FDA approval. So, there’s a lot of anecdotal evidence. There’s a lot of really great research that has been done out of Harvard and out of Rensselaer Polytechnic Institute, both amazing programs who are on the leading edge of that. So, we do have a lot of feedback about a mindful system really producing, improving health and productivity and user satisfaction. But the only thing we should be careful about in the meantime as we start applying these is promising those benefits. Because while the research is there, I am not a medical professional so I cannot guarantee you those results. (J: Right.) I know that we can’t make any claims directly that ‘hey put this lighting in your space and (J: Right, put blue lighting…) and never get cancer’… Because I am not a doctor, I’m not a health care professional, but we have seen a lot of correlations and there is a lot of research out there that we can help improve, not just your wellness and your mood, but also your health in the long run by having access to healthy lighting. (J: Right.) But we have seen those correlations and there is enough knowledge in our user populations where they are already asking. And this is something they’re interested in. They know the benefit to themselves. So, there’s enough research to keep moving. Just be careful about what we promise.

Janet: … what we’re promising, right. Well it’s interesting. I mean, like you said, there’s been all sorts of research, there’s, but a lot of it seems to be the aftermath that they look at as anecdotal (C: Yes) there seem to be very, there doesn’t seem to be a lot of concrete evidence that data, that data shows that there’s a direct correlation. I think, it seems pretty obvious. I think it should be and I think you know because maybe of the advent of electricity we have had some real departure and has, you know, the electricity has given us a lot of benefits and helped us to live longer but I think it’s also been problematic in terms of how we conduct our lives. And I mean I know I can stay up pretty late and watch television and everything gets a little wonky for a while. But I find that all of that is, kind of just a kind of interesting. There’s, the studies that came out of, I want to say there’s a town in Japan and I think someplace in Helsinki, both who have taken their blue lights and their streetlights and changed them into some sort of Amber lighting some sort of… I can’t, you could have… (C: back to high pressure sodium.)

Janet: Oh… is that a lighting joke, I don’t know…

Catherine: It is a lighting a joke. I am such a nerd (J: I know) it would be back to the sources we were using before, which were very yellow. They, if you have, my car has a red and blue dial that tells me the temperature and in a couple of our tunnels around here that dial looks like two colors of grey. It’s because high pressure sodium it’s got only warm light and so specific of a spectrum that it doesn’t even hit the Reds. So, you can’t see red you can’t see blue. It’s a very narrow in the spectral power distribution and look like a needle. It’s right up and down on that specific nanometer. So, it’s great for nighttime lighting to not stimulate your circadian system but it’s not very efficient. So, I think we’ve gained a lot of efficiency, and it looks so nice and bright and clean with the really blue LED streetlights, but we didn’t need that much light and it’s possibly keeping us up later at night.

Janet: Catherine, (C: Yes.) Before I let you go. Are there any other specific examples you would like to give the listener about healthy lighting and what you would do as a designer to create healthy lighting for people.

Catherine: Sure, yes. A couple of things come to mind. Not just improving, I think, improved light levels and full spectrum sources, especially in health care, is very important. To have that a full morning of light exposure which helps to bring them back to a 24-hour daytime. That has actually many evidences to improving recovery time. So, if your room does not have access to daylight, absolutely, we want to provide a system that’s capable of mimicking the daylight effect on your circadian system. And then, we need to go a little step further and actually think about finishes. If I have a red wall, I’m not reflecting any blue light off that red wall. It was absorbed. I’m only reflecting the red light, (J: Okay), the red spectrum. So that choice of color of wall is influencing the efficiency of the light (J: of the light). Yes. And not just from a luminate standpoint, I could still read just fine under it. It just has much less of an impact on my non-visual system. So, moving a little bit further into finishes and, for the office environment as well, partition heights, bringing that down which is a movement on the WELL side and LEED as well… (J: Right) is allowing better light sharing between spaces and especially daylight penetration into this space.

Janet: Right, well, I think that that’s kind of fascinating and for the listeners out there, if they need any more information on healthy lighting, we all know where to go to. And Catherine thank you so much for being with us this afternoon.

Catherine: Thank you for having me, this is lots of fun.

Janet: Great, Thank you. If you would like to contact Catherine or get any other information and resources that we have talked about today, please go to Thank you very much. Thank you so much Catherine for being here today.

Catherine: Thanks Janet.

(Music- transition to Outro)

Carolyn: We hope you enjoy our Inclusive Designers Podcast and forum.

Janet: For more information on our guests, or on the design and research covered in this episode, please check out our webpage at:

Carolyn: If you have any questions on today’s topic or have suggestions for future topics you’d like us to include, please shoot us an email at:

Janet: And we look forward to your feedback as well. Until our next podcast episode… Stay well and stay well informed. Thanks again for listening.

Carolyn: Thanks again.

In this photo, Catherine is wearing a light sensor prototype for a month long study of the health of her circadian system as part of the RPI ‘Light and Health’ intensive.

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