CE Pro September 2024 - 26

Lighting
FIXTURES | CONTROLS | MOTORIZED SHADES
Reconsidering
Circadian vs.
Human-Centric
Lighting
By David Warfel
WHAT IS CIRCADIAN
lighting? What is human-centric
lighting? And
why should we care?
First, let's establish a baseline
that we can call " normal
lighting. " We've taken light,
stripped its beauty, magic,
and health benefits, and then
pushed the freeze button to
make sure it never changed.
This is our current normal.
Circadian lighting is not
normal. I am going to define
it as lighting that is fully
synchronized with daylight.
When the sun rises, circadian
lighting turns on at a bright
warm glow. When the sun
hits the middle of the sky at
noon, circadian lighting is at
its brightest and bluest. As
the sun moves lower on the
horizon, circadian lighting
begins to dim and warm towards
sunset. And when the
sun sets, and the sky is dark,
circadian lighting is turned
off and completely dark.
In other words, circadian
lighting is natural lighting,
electrified and brought
indoors, fully synchronized
with what is happening
outside. For a few years, I
thought this was the ideal
26 | CE Pro September 2024
solution to lighting problems.
Then I saw the results
and was deeply unsatisfied
but could not immediately
put my finger on why.
I know now why I disliked
those early adoptions of circadian
lighting, and the answer
is somewhat complicated
and at the same time simple:
synchronization with daylight
does not work well for our societal
needs, and unified color
temperatures are like living
in a sepia-toned photograph
from the late 1800s.
Enter human-centric
lighting (HCL). To me, HCL
is a careful balance of our
bodies' biological need for
natural light and our societal
demands for increased productivity
and extended play.
HCL mimics, without strict
adherence, the rise and fall
of the sun and changing seasons
while giving us enough
light to do what we need
to do. And it recognizes our
desire - perhaps our need
- for dynamic variety.
If circadian lighting brightens
when the sun rises, HCL
brightens when we rise,
effectively making sunrise
happen on our schedule
Our quest for " natural light " has taken us further from it.
instead of the universe's.
Personally, I would love to
wake with the sun and go to
sleep with natural darkness,
but there are good portions
of the year where that would
make for very short days and
very long nights.
If I lived with circadian
lighting in a Wisconsin winter,
I would wake up around 8
a.m., show up for work about
10 a.m. and clock out around
2 p.m. so I could eat dinner,
finish my chores, and go back
to bed around 5. My schedule
would be a little bit different
every day, depending on
weather and the change of
natural light, and that might
make it hard to schedule
meetings. Given that I am, in
this scenario, working a fourhour
day minus a lunch break,
that's going to make it tough
to meet deadlines.
I would rather have HCL
that begins to glow around 5
a.m., gently wakes me without
an alarm around 5:30, energizes
me from 8 a.m. until 5 p.m.,
and then gradually dims to
prepare me for sleep around 9.
We need light to see what
we are doing, and that can
mean anything from shaving
at 6:30 a.m. to reading a
book at 9 p.m. Circadian
lighting doesn't care what
light we need to for task, it
simply cares about what the
sun is (or is not) doing. This
does not work very well for
human lifestyles.
Circadian lighting, at
least the variety that
matches all color temperatures
in a space and
synchronizes them with
sunlight, looks ugly to me.
Unified color temperatures
look bad because they are
decidedly unnatural. Our
quest for " natural light "
has taken us further from
it by stripping out the
dynamic variety.
DAVID WARFEL is Chief
Evangelist of Light at
design firm Light Can Help
You (lightcanhelpyou.com).
cepro.com
YAVOR/STOCK.ADOBE.COM
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CE Pro September 2024

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