The LONVIA Edit
Curated insights on space, health, investment, and the future of living.
Science
Your home has two lighting problems, and they are opposites
The LONVIA
Edit
Curated insights on space, health, investment, and the future of living.
Science
Your home has two lighting problems, and they are opposites
6 min read
Most homes fail the body twice a day in opposite directions. During daylight hours they deliver far less biological signal than the consensus threshold of 250 mEDI lux. After sunset the same fixtures deliver several times more than the 10 mEDI lux ceiling. The light itself barely changes. What changes is what the body needs from it.
Why is a bright-looking room still too dim for your body?
Because your eye and your clock are reading different things.
Vision adapts. Step indoors from an overcast morning and the room resolves within seconds, so it registers as adequately lit. The adaptation is a perceptual adjustment, not a measurement. The circadian system performs no such correction. It responds to the melanopic content actually arriving at the eye, quantified as melanopic equivalent daylight illuminance, or mEDI, under CIE S 026:2018.
The two readings diverge sharply. Outdoor illuminance on a grey, overcast morning still runs into the thousands of lux. A well-lit domestic interior typically sits in the low hundreds. Around 90 per cent of the day is spent indoors, commonly under 200 mEDI lux at the eye, against a recommended daytime minimum of 250 mEDI lux in Brown et al. 2022.
So the room looks fine and reads as night-adjacent. The signal that should say daytime is arriving at roughly a third of strength.
Why does the same fixture become a problem after sunset?
Because at that hour the requirement inverts, and the fixture does not.
Brown et al. 2022 sets the evening target below 10 mEDI lux in the three hours before sleep, and 1 mEDI lux or less during it. A ceiling fitting at ordinary domestic brightness does not approach that. A warm 2700K source at usable room levels commonly delivers somewhere between 45 and 90 mEDI lux, which is four to nine times the evening ceiling.
Two design habits make it worse. Overhead placement points the source directly into the visual field from above, which is close to the geometry the retina is most exposed to. And brightness falls with the square of distance, so a fitting three metres up must run far harder than a low lamp at arm’s length to light the same task. The ceiling is the least efficient place to put evening light and the most biologically expensive.
Dimming helps less than people expect. Reducing output lowers the number. It does not alter the spectral composition producing it. Warm and dim is a visual description. It is not a biological one.
Why can one fixed light not do both jobs?
Because the two jobs are not points on one scale. They are opposing requirements.
Morning asks for a strong, sustained signal. Evening asks for near silence. A fixture with a single fixed spectral output can be positioned well for one of those and will then be wrong for the other, every day, for as long as it is installed. Dimmers move brightness along one axis. The biology is asking for a different axis entirely.
This is the problem LONVIA exists to address. Not brighter light, and not dimmer light. Light that behaves differently at different hours because the body’s requirement does.
What can you change tomorrow at no cost?
Two adjustments, both free, both larger in effect than most people assume.
In the morning, go outside during your first waking hour. Even under heavy cloud, outdoor illuminance exceeds anything a domestic interior provides. Ten to twenty minutes outdoors delivers a stronger daytime signal than a full morning beside a window. Grey weather is not a reason to skip it. The gap between outdoors and indoors remains large in almost any daylight condition.
At night, turn the ceiling light off. Use the warmest, dimmest lamp you own, placed low and close to where you are sitting. Low placement keeps the source out of the upper visual field. Proximity means a lower output produces the same usable light. Both reduce what reaches the eye without leaving you in the dark.
Neither is a replacement for correct light. Both narrow the gap measurably, tonight, with what is already in the room.
What does this change about how you judge a lamp?
It changes the question from how a lamp looks to what it delivers, and when.
The specification that matters is mEDI at the eye, stated separately for daytime and evening, at a realistic viewing distance. Not lumens. Not colour temperature, which describes appearance rather than melanopic content. Not a dimming range, which moves one variable and leaves the other untouched.
Almost no product on the market is specified that way. That absence is the whole opportunity, and it is why this publication keeps returning to a single number.
With light,
Roksana Fasovska
LONVIA Founder
Frequently asked questions
How much daytime light does the scientific consensus recommend?
Brown et al. 2022 recommends a minimum of 250 mEDI lux at the eye during daytime hours. Most homes deliver roughly one third of that.
How dim should light be in the evening?
Below 10 mEDI lux in the three hours before sleep, and at or below 1 mEDI lux during sleep, according to the same consensus.
Does dimming a warm bulb make it safe for the evening?
Dimming reduces output, which lowers mEDI, but it does not change spectral composition. A dimmed warm source at functional room brightness frequently remains above the 10 mEDI evening threshold.
Is morning outdoor light still worth it on a cloudy day?
Yes. Outdoor illuminance under overcast conditions remains far above indoor levels, so the daytime signal is substantially stronger outside regardless of cloud cover.
References
1. Brown TM, Brainard GJ, Cajochen C, et al. Recommendations for daytime, evening, and night-time indoor light exposure to best support physiology, sleep, and wakefulness in healthy adults. PLOS Biology. 2022;20(3):e3001571.
2. International Commission on Illumination (CIE). CIE S 026/E:2018. CIE System for Metrology of Optical Radiation for ipRGC-Influenced Responses to Light. Vienna: CIE; 2018.
3. Zeitzer JM, Dijk DJ, Kronauer RE, Brown EN, Czeisler CA. Sensitivity of the human circadian pacemaker to nocturnal light: melatonin phase resetting and suppression. Journal of Physiology. 2000;526(3):695-702.
4. Phillips AJK, Vidafar P, Burns AC, et al. High sensitivity and interindividual variability in the response of the human circadian system to evening light. Proceedings of the National Academy of Sciences of the United States of America. 2019;116(24):12019-12024.
5. Mason IC, Grimaldi D, Reid KJ, et al. Light exposure during sleep impairs cardiometabolic function. Proceedings of the National Academy of Sciences of the United States of America. 2022;119(12):e2113290119.
Ready to shape a healthier future?
Book an introductory conversation to explore how well-being can be integrated into your space or project
Ready to shape a healthier future?
Book an introductory conversation to explore how well-being can be integrated into your space or project
Ready to shape a healthier future?
Book an introductory conversation to explore how well-being can be integrated into your space or project
6 min read
Key Insight
Most homes fail the body twice a day in opposite directions. During daylight hours they deliver far less biological signal than the consensus threshold of 250 mEDI lux. After sunset the same fixtures deliver several times more than the 10 mEDI lux ceiling. The light itself barely changes. What changes is what the body needs from it.
Most homes fail the body twice a day in opposite directions. During daylight hours they deliver far less biological signal than the consensus threshold of 250 mEDI lux. After sunset the same fixtures deliver several times more than the 10 mEDI lux ceiling. The light itself barely changes. What changes is what the body needs from it.
Why is a bright-looking room still too dim for your body?
Because your eye and your clock are reading different things.
Vision adapts. Step indoors from an overcast morning and the room resolves within seconds, so it registers as adequately lit. The adaptation is a perceptual adjustment, not a measurement. The circadian system performs no such correction. It responds to the melanopic content actually arriving at the eye, quantified as melanopic equivalent daylight illuminance, or mEDI, under CIE S 026:2018.
The two readings diverge sharply. Outdoor illuminance on a grey, overcast morning still runs into the thousands of lux. A well-lit domestic interior typically sits in the low hundreds. Around 90 per cent of the day is spent indoors, commonly under 200 mEDI lux at the eye, against a recommended daytime minimum of 250 mEDI lux in Brown et al. 2022.
So the room looks fine and reads as night-adjacent. The signal that should say daytime is arriving at roughly a third of strength.
Why does the same fixture become a problem after sunset?
Because at that hour the requirement inverts, and the fixture does not.
Brown et al. 2022 sets the evening target below 10 mEDI lux in the three hours before sleep, and 1 mEDI lux or less during it. A ceiling fitting at ordinary domestic brightness does not approach that. A warm 2700K source at usable room levels commonly delivers somewhere between 45 and 90 mEDI lux, which is four to nine times the evening ceiling.
Two design habits make it worse. Overhead placement points the source directly into the visual field from above, which is close to the geometry the retina is most exposed to. And brightness falls with the square of distance, so a fitting three metres up must run far harder than a low lamp at arm’s length to light the same task. The ceiling is the least efficient place to put evening light and the most biologically expensive.
Dimming helps less than people expect. Reducing output lowers the number. It does not alter the spectral composition producing it. Warm and dim is a visual description. It is not a biological one.
Why does the same fixture become a problem after sunset?
Because at that hour the requirement inverts, and the fixture does not.
Brown et al. 2022 sets the evening target below 10 mEDI lux in the three hours before sleep, and 1 mEDI lux or less during it. A ceiling fitting at ordinary domestic brightness does not approach that. A warm 2700K source at usable room levels commonly delivers somewhere between 45 and 90 mEDI lux, which is four to nine times the evening ceiling.
Two design habits make it worse. Overhead placement points the source directly into the visual field from above, which is close to the geometry the retina is most exposed to. And brightness falls with the square of distance, so a fitting three metres up must run far harder than a low lamp at arm’s length to light the same task. The ceiling is the least efficient place to put evening light and the most biologically expensive.
Dimming helps less than people expect. Reducing output lowers the number. It does not alter the spectral composition producing it. Warm and dim is a visual description. It is not a biological one.
Why does the same fixture become a problem after sunset?
Because at that hour the requirement inverts, and the fixture does not.
Brown et al. 2022 sets the evening target below 10 mEDI lux in the three hours before sleep, and 1 mEDI lux or less during it. A ceiling fitting at ordinary domestic brightness does not approach that. A warm 2700K source at usable room levels commonly delivers somewhere between 45 and 90 mEDI lux, which is four to nine times the evening ceiling.
Two design habits make it worse. Overhead placement points the source directly into the visual field from above, which is close to the geometry the retina is most exposed to. And brightness falls with the square of distance, so a fitting three metres up must run far harder than a low lamp at arm’s length to light the same task. The ceiling is the least efficient place to put evening light and the most biologically expensive.
Dimming helps less than people expect. Reducing output lowers the number. It does not alter the spectral composition producing it. Warm and dim is a visual description. It is not a biological one.
Why is a bright-looking room still too dim for your body?
Because your eye and your clock are reading different things.
Vision adapts. Step indoors from an overcast morning and the room resolves within seconds, so it registers as adequately lit. The adaptation is a perceptual adjustment, not a measurement. The circadian system performs no such correction. It responds to the melanopic content actually arriving at the eye, quantified as melanopic equivalent daylight illuminance, or mEDI, under CIE S 026:2018.
The two readings diverge sharply. Outdoor illuminance on a grey, overcast morning still runs into the thousands of lux. A well-lit domestic interior typically sits in the low hundreds. Around 90 per cent of the day is spent indoors, commonly under 200 mEDI lux at the eye, against a recommended daytime minimum of 250 mEDI lux in Brown et al. 2022.
So the room looks fine and reads as night-adjacent. The signal that should say daytime is arriving at roughly a third of strength.
Why can one fixed light not do both jobs?
Because the two jobs are not points on one scale. They are opposing requirements.
Morning asks for a strong, sustained signal. Evening asks for near silence. A fixture with a single fixed spectral output can be positioned well for one of those and will then be wrong for the other, every day, for as long as it is installed. Dimmers move brightness along one axis. The biology is asking for a different axis entirely.
This is the problem LONVIA exists to address. Not brighter light, and not dimmer light. Light that behaves differently at different hours because the body’s requirement does.
Why can one fixed light not do both jobs?
Because the two jobs are not points on one scale. They are opposing requirements.
Morning asks for a strong, sustained signal. Evening asks for near silence. A fixture with a single fixed spectral output can be positioned well for one of those and will then be wrong for the other, every day, for as long as it is installed. Dimmers move brightness along one axis. The biology is asking for a different axis entirely.
This is the problem LONVIA exists to address. Not brighter light, and not dimmer light. Light that behaves differently at different hours because the body’s requirement does.
What can you change tomorrow at no cost?
Two adjustments, both free, both larger in effect than most people assume.
In the morning, go outside during your first waking hour. Even under heavy cloud, outdoor illuminance exceeds anything a domestic interior provides. Ten to twenty minutes outdoors delivers a stronger daytime signal than a full morning beside a window. Grey weather is not a reason to skip it. The gap between outdoors and indoors remains large in almost any daylight condition.
At night, turn the ceiling light off. Use the warmest, dimmest lamp you own, placed low and close to where you are sitting. Low placement keeps the source out of the upper visual field. Proximity means a lower output produces the same usable light. Both reduce what reaches the eye without leaving you in the dark.
Neither is a replacement for correct light. Both narrow the gap measurably, tonight, with what is already in the room.
What can you change tomorrow at no cost?
Two adjustments, both free, both larger in effect than most people assume.
In the morning, go outside during your first waking hour. Even under heavy cloud, outdoor illuminance exceeds anything a domestic interior provides. Ten to twenty minutes outdoors delivers a stronger daytime signal than a full morning beside a window. Grey weather is not a reason to skip it. The gap between outdoors and indoors remains large in almost any daylight condition.
At night, turn the ceiling light off. Use the warmest, dimmest lamp you own, placed low and close to where you are sitting. Low placement keeps the source out of the upper visual field. Proximity means a lower output produces the same usable light. Both reduce what reaches the eye without leaving you in the dark.
Neither is a replacement for correct light. Both narrow the gap measurably, tonight, with what is already in the room.
What does this change about how you judge a lamp?
It changes the question from how a lamp looks to what it delivers, and when.
The specification that matters is mEDI at the eye, stated separately for daytime and evening, at a realistic viewing distance. Not lumens. Not colour temperature, which describes appearance rather than melanopic content. Not a dimming range, which moves one variable and leaves the other untouched.
Almost no product on the market is specified that way. That absence is the whole opportunity, and it is why this publication keeps returning to a single number.
What does this change about how you judge a lamp?
It changes the question from how a lamp looks to what it delivers, and when.
The specification that matters is mEDI at the eye, stated separately for daytime and evening, at a realistic viewing distance. Not lumens. Not colour temperature, which describes appearance rather than melanopic content. Not a dimming range, which moves one variable and leaves the other untouched.
Almost no product on the market is specified that way. That absence is the whole opportunity, and it is why this publication keeps returning to a single number.
Frequently asked questions
How much daytime light does the scientific consensus recommend?
Brown et al. 2022 recommends a minimum of 250 mEDI lux at the eye during daytime hours. Most homes deliver roughly one third of that.
How dim should light be in the evening?
Below 10 mEDI lux in the three hours before sleep, and at or below 1 mEDI lux during sleep, according to the same consensus.
Does dimming a warm bulb make it safe for the evening?
Dimming reduces output, which lowers mEDI, but it does not change spectral composition. A dimmed warm source at functional room brightness frequently remains above the 10 mEDI evening threshold.
Is morning outdoor light still worth it on a cloudy day?
Yes. Outdoor illuminance under overcast conditions remains far above indoor levels, so the daytime signal is substantially stronger outside regardless of cloud cover.
References
1. Brown TM, Brainard GJ, Cajochen C, et al. Recommendations for daytime, evening, and night-time indoor light exposure to best support physiology, sleep, and wakefulness in healthy adults. PLOS Biology. 2022;20(3):e3001571.
2. International Commission on Illumination (CIE). CIE S 026/E:2018. CIE System for Metrology of Optical Radiation for ipRGC-Influenced Responses to Light. Vienna: CIE; 2018.
3. Zeitzer JM, Dijk DJ, Kronauer RE, Brown EN, Czeisler CA. Sensitivity of the human circadian pacemaker to nocturnal light: melatonin phase resetting and suppression. Journal of Physiology. 2000;526(3):695-702.
4. Phillips AJK, Vidafar P, Burns AC, et al. High sensitivity and interindividual variability in the response of the human circadian system to evening light. Proceedings of the National Academy of Sciences of the United States of America. 2019;116(24):12019-12024.
5. Mason IC, Grimaldi D, Reid KJ, et al. Light exposure during sleep impairs cardiometabolic function. Proceedings of the National Academy of Sciences of the United States of America. 2022;119(12):e2113290119.
References
1. Brown TM, Brainard GJ, Cajochen C, et al. Recommendations for daytime, evening, and night-time indoor light exposure to best support physiology, sleep, and wakefulness in healthy adults. PLOS Biology. 2022;20(3):e3001571.
2. International Commission on Illumination (CIE). CIE S 026/E:2018. CIE System for Metrology of Optical Radiation for ipRGC-Influenced Responses to Light. Vienna: CIE; 2018.
3. Zeitzer JM, Dijk DJ, Kronauer RE, Brown EN, Czeisler CA. Sensitivity of the human circadian pacemaker to nocturnal light: melatonin phase resetting and suppression. Journal of Physiology. 2000;526(3):695-702.
4. Phillips AJK, Vidafar P, Burns AC, et al. High sensitivity and interindividual variability in the response of the human circadian system to evening light. Proceedings of the National Academy of Sciences of the United States of America. 2019;116(24):12019-12024.
5. Mason IC, Grimaldi D, Reid KJ, et al. Light exposure during sleep impairs cardiometabolic function. Proceedings of the National Academy of Sciences of the United States of America. 2022;119(12):e2113290119.
With light,
Roksana Fasovska
Roksana Fasovska
LONVIA Founder
Science
Your home has two lighting problems, and they are opposites
6 min read
Most homes fail the body twice a day in opposite directions. During daylight hours they deliver far less biological signal than the consensus threshold of 250 mEDI lux. After sunset the same fixtures deliver several times more than the 10 mEDI lux ceiling. The light itself barely changes. What changes is what the body needs from it.
Key Insight
Why is a bright-looking room still too dim for your body?
Because your eye and your clock are reading different things.
Vision adapts. Step indoors from an overcast morning and the room resolves within seconds, so it registers as adequately lit. The adaptation is a perceptual adjustment, not a measurement. The circadian system performs no such correction. It responds to the melanopic content actually arriving at the eye, quantified as melanopic equivalent daylight illuminance, or mEDI, under CIE S 026:2018.
The two readings diverge sharply. Outdoor illuminance on a grey, overcast morning still runs into the thousands of lux. A well-lit domestic interior typically sits in the low hundreds. Around 90 per cent of the day is spent indoors, commonly under 200 mEDI lux at the eye, against a recommended daytime minimum of 250 mEDI lux in Brown et al. 2022.
So the room looks fine and reads as night-adjacent. The signal that should say daytime is arriving at roughly a third of strength.
Why does the same fixture become a problem after sunset?
Because at that hour the requirement inverts, and the fixture does not.
Brown et al. 2022 sets the evening target below 10 mEDI lux in the three hours before sleep, and 1 mEDI lux or less during it. A ceiling fitting at ordinary domestic brightness does not approach that. A warm 2700K source at usable room levels commonly delivers somewhere between 45 and 90 mEDI lux, which is four to nine times the evening ceiling.
Two design habits make it worse. Overhead placement points the source directly into the visual field from above, which is close to the geometry the retina is most exposed to. And brightness falls with the square of distance, so a fitting three metres up must run far harder than a low lamp at arm’s length to light the same task. The ceiling is the least efficient place to put evening light and the most biologically expensive.
Dimming helps less than people expect. Reducing output lowers the number. It does not alter the spectral composition producing it. Warm and dim is a visual description. It is not a biological one.
Why does the same fixture become a problem after sunset?
Because at that hour the requirement inverts, and the fixture does not.
Brown et al. 2022 sets the evening target below 10 mEDI lux in the three hours before sleep, and 1 mEDI lux or less during it. A ceiling fitting at ordinary domestic brightness does not approach that. A warm 2700K source at usable room levels commonly delivers somewhere between 45 and 90 mEDI lux, which is four to nine times the evening ceiling.
Two design habits make it worse. Overhead placement points the source directly into the visual field from above, which is close to the geometry the retina is most exposed to. And brightness falls with the square of distance, so a fitting three metres up must run far harder than a low lamp at arm’s length to light the same task. The ceiling is the least efficient place to put evening light and the most biologically expensive.
Dimming helps less than people expect. Reducing output lowers the number. It does not alter the spectral composition producing it. Warm and dim is a visual description. It is not a biological one.
Why does the same fixture become a problem after sunset?
Because at that hour the requirement inverts, and the fixture does not.
Brown et al. 2022 sets the evening target below 10 mEDI lux in the three hours before sleep, and 1 mEDI lux or less during it. A ceiling fitting at ordinary domestic brightness does not approach that. A warm 2700K source at usable room levels commonly delivers somewhere between 45 and 90 mEDI lux, which is four to nine times the evening ceiling.
Two design habits make it worse. Overhead placement points the source directly into the visual field from above, which is close to the geometry the retina is most exposed to. And brightness falls with the square of distance, so a fitting three metres up must run far harder than a low lamp at arm’s length to light the same task. The ceiling is the least efficient place to put evening light and the most biologically expensive.
Dimming helps less than people expect. Reducing output lowers the number. It does not alter the spectral composition producing it. Warm and dim is a visual description. It is not a biological one.
Why is a bright-looking room still too dim for your body?
Because your eye and your clock are reading different things.
Vision adapts. Step indoors from an overcast morning and the room resolves within seconds, so it registers as adequately lit. The adaptation is a perceptual adjustment, not a measurement. The circadian system performs no such correction. It responds to the melanopic content actually arriving at the eye, quantified as melanopic equivalent daylight illuminance, or mEDI, under CIE S 026:2018.
The two readings diverge sharply. Outdoor illuminance on a grey, overcast morning still runs into the thousands of lux. A well-lit domestic interior typically sits in the low hundreds. Around 90 per cent of the day is spent indoors, commonly under 200 mEDI lux at the eye, against a recommended daytime minimum of 250 mEDI lux in Brown et al. 2022.
So the room looks fine and reads as night-adjacent. The signal that should say daytime is arriving at roughly a third of strength.
Why can one fixed light not do both jobs?
Because the two jobs are not points on one scale. They are opposing requirements.
Morning asks for a strong, sustained signal. Evening asks for near silence. A fixture with a single fixed spectral output can be positioned well for one of those and will then be wrong for the other, every day, for as long as it is installed. Dimmers move brightness along one axis. The biology is asking for a different axis entirely.
This is the problem LONVIA exists to address. Not brighter light, and not dimmer light. Light that behaves differently at different hours because the body’s requirement does.
Why can one fixed light not do both jobs?
Because the two jobs are not points on one scale. They are opposing requirements.
Morning asks for a strong, sustained signal. Evening asks for near silence. A fixture with a single fixed spectral output can be positioned well for one of those and will then be wrong for the other, every day, for as long as it is installed. Dimmers move brightness along one axis. The biology is asking for a different axis entirely.
This is the problem LONVIA exists to address. Not brighter light, and not dimmer light. Light that behaves differently at different hours because the body’s requirement does.
What can you change tomorrow at no cost?
Two adjustments, both free, both larger in effect than most people assume.
In the morning, go outside during your first waking hour. Even under heavy cloud, outdoor illuminance exceeds anything a domestic interior provides. Ten to twenty minutes outdoors delivers a stronger daytime signal than a full morning beside a window. Grey weather is not a reason to skip it. The gap between outdoors and indoors remains large in almost any daylight condition.
At night, turn the ceiling light off. Use the warmest, dimmest lamp you own, placed low and close to where you are sitting. Low placement keeps the source out of the upper visual field. Proximity means a lower output produces the same usable light. Both reduce what reaches the eye without leaving you in the dark.
Neither is a replacement for correct light. Both narrow the gap measurably, tonight, with what is already in the room.
What can you change tomorrow at no cost?
Two adjustments, both free, both larger in effect than most people assume.
In the morning, go outside during your first waking hour. Even under heavy cloud, outdoor illuminance exceeds anything a domestic interior provides. Ten to twenty minutes outdoors delivers a stronger daytime signal than a full morning beside a window. Grey weather is not a reason to skip it. The gap between outdoors and indoors remains large in almost any daylight condition.
At night, turn the ceiling light off. Use the warmest, dimmest lamp you own, placed low and close to where you are sitting. Low placement keeps the source out of the upper visual field. Proximity means a lower output produces the same usable light. Both reduce what reaches the eye without leaving you in the dark.
Neither is a replacement for correct light. Both narrow the gap measurably, tonight, with what is already in the room.
What does this change about how you judge a lamp?
It changes the question from how a lamp looks to what it delivers, and when.
The specification that matters is mEDI at the eye, stated separately for daytime and evening, at a realistic viewing distance. Not lumens. Not colour temperature, which describes appearance rather than melanopic content. Not a dimming range, which moves one variable and leaves the other untouched.
Almost no product on the market is specified that way. That absence is the whole opportunity, and it is why this publication keeps returning to a single number.
What does this change about how you judge a lamp?
It changes the question from how a lamp looks to what it delivers, and when.
The specification that matters is mEDI at the eye, stated separately for daytime and evening, at a realistic viewing distance. Not lumens. Not colour temperature, which describes appearance rather than melanopic content. Not a dimming range, which moves one variable and leaves the other untouched.
Almost no product on the market is specified that way. That absence is the whole opportunity, and it is why this publication keeps returning to a single number.
Frequently asked questions
How much daytime light does the scientific consensus recommend?
Brown et al. 2022 recommends a minimum of 250 mEDI lux at the eye during daytime hours. Most homes deliver roughly one third of that.
How dim should light be in the evening?
Below 10 mEDI lux in the three hours before sleep, and at or below 1 mEDI lux during sleep, according to the same consensus.
Does dimming a warm bulb make it safe for the evening?
Dimming reduces output, which lowers mEDI, but it does not change spectral composition. A dimmed warm source at functional room brightness frequently remains above the 10 mEDI evening threshold.
Is morning outdoor light still worth it on a cloudy day?
Yes. Outdoor illuminance under overcast conditions remains far above indoor levels, so the daytime signal is substantially stronger outside regardless of cloud cover.
References
1. Brown TM, Brainard GJ, Cajochen C, et al. Recommendations for daytime, evening, and night-time indoor light exposure to best support physiology, sleep, and wakefulness in healthy adults. PLOS Biology. 2022;20(3):e3001571.
2. International Commission on Illumination (CIE). CIE S 026/E:2018. CIE System for Metrology of Optical Radiation for ipRGC-Influenced Responses to Light. Vienna: CIE; 2018.
3. Zeitzer JM, Dijk DJ, Kronauer RE, Brown EN, Czeisler CA. Sensitivity of the human circadian pacemaker to nocturnal light: melatonin phase resetting and suppression. Journal of Physiology. 2000;526(3):695-702.
4. Phillips AJK, Vidafar P, Burns AC, et al. High sensitivity and interindividual variability in the response of the human circadian system to evening light. Proceedings of the National Academy of Sciences of the United States of America. 2019;116(24):12019-12024.
5. Mason IC, Grimaldi D, Reid KJ, et al. Light exposure during sleep impairs cardiometabolic function. Proceedings of the National Academy of Sciences of the United States of America. 2022;119(12):e2113290119.
References
1. Brown TM, Brainard GJ, Cajochen C, et al. Recommendations for daytime, evening, and night-time indoor light exposure to best support physiology, sleep, and wakefulness in healthy adults. PLOS Biology. 2022;20(3):e3001571.
2. International Commission on Illumination (CIE). CIE S 026/E:2018. CIE System for Metrology of Optical Radiation for ipRGC-Influenced Responses to Light. Vienna: CIE; 2018.
3. Zeitzer JM, Dijk DJ, Kronauer RE, Brown EN, Czeisler CA. Sensitivity of the human circadian pacemaker to nocturnal light: melatonin phase resetting and suppression. Journal of Physiology. 2000;526(3):695-702.
4. Phillips AJK, Vidafar P, Burns AC, et al. High sensitivity and interindividual variability in the response of the human circadian system to evening light. Proceedings of the National Academy of Sciences of the United States of America. 2019;116(24):12019-12024.
5. Mason IC, Grimaldi D, Reid KJ, et al. Light exposure during sleep impairs cardiometabolic function. Proceedings of the National Academy of Sciences of the United States of America. 2022;119(12):e2113290119.
Roksana Fasovska
LONVIA Founder
With light,