Here in the U.

S., a good 40% of all  the energy we use goes into buildings. Like, not the construction of buildings.

Just… the existence of buildings. Sitting there with their lights  on, and their appliances humming, and their climate-controlled air. And if we want to have any hope  of dialing back our energy usage, we have to rethink our buildings The good news is, we are.

Many new buildings have special  windows meant to keep things cool by letting some light in and blocking the rest. But we’re just starting to learn  how certain wavelengths in sunlight, even invisible ones, can be  really important for our health. They can help with conditions ranging from  nearsightedness to COVID to Alzheimer's.

This is terrible news for me as a person who  loves to just work in the dark, all of the time. And this begs the question: Are  energy-efficient windows bad for us? [♪ INTRO] Energy-efficient windows are basically  like sunglasses for buildings. They filter out some of the Sun’s rays and make things more  comfortable on the other side.

One way to do this is with a  low-emissivity coating, or a low-e coating. This coating mainly reflects  infrared waves, which carry heat. It keeps outside heat from  coming in during the summer, and indoor heat from escaping during the winter.

Low-e coatings also filter out  almost all of the Sun’s UV light. That doesn’t help much with keeping things cool, but it does help protect furniture  and decorations from fading. So low-e materials are great for saving  energy and protecting indoor environments.

But these savings come with some  downsides for the people behind the glass. Almost every cell in our bodies  follows a circadian rhythm that aligns with the 24-hour  cycle of day and night. And it’s not just responsible for the  jetlag we get after an overseas flight.

Circadian rhythms also control our  sleep patterns, appetites, hormones, and a bunch of other biological functions. So it’s really important for all these  cellular clocks to stay synced up. Our cells take their main cue from the Sun, syncing up with the 24-hour pattern  of light and dark here on Earth.

They respond especially strongly to blue light, which activates special pigments in our eyes. The problem is that the same film  that block UV and infrared light also filter out a good amount  of blue and violet light. So if you’re sitting behind some  of this fancy glass all day, you may not be getting all the cues  you need to tune your circadian rhythm.

And that could be a problem. Disrupted circadian rhythms have been linked with higher rates of heart disease,  diabetes, and obesity. They may also be behind an uptick  in nearsightedness, or myopia.

Nearly a third of all people are now nearsighted, and myopia is becoming more  common all around the world. And there’s a reason researchers suspect this  could have something to do with our windows. One study found that rates of  myopia are lower in rural areas, where people spend more time  outside compared to urban areas.

Another study found that when mice were  exposed to violet light in the lab, they had lower rates of myopia than mice exposed to regular fluorescent  lights or other wavelengths. But as for why this is,  researchers aren’t sure yet. What we do know is that in the retina, special pigments called neuropsins  get activated by violet light.

And that helps the circadian rhythm of  these cells, which controls how they function. In nearsighted people, one  layer of cells in the retina, called the choroid, tends  to be thinner than normal. So, it’s possible that our scrambled  circadian rhythms are messing with the development of the choroid,  making so many of us nearsighted.

The way that we’re going,  the World Health Organization predicts that half of all people  will be nearsighted by 2050. At the same time, we may be missing out on important benefits from the  other end of the spectrum. Because infrared light can  also be good for our health.

One thing it can do is help  our bodies reduce inflammation. While inflammation is part of our  body’s natural healing process, too much of it can cause serious damage. For example, most COVID deaths  are not caused by the virus itself but by severe inflammation, which creates  respiratory problems and other issues.

So, in cases like this, reducing  inflammation can be life-saving. And infrared light therapy has already  been helpful in treating severe COVID and other conditions caused  by severe inflammation. The weird thing is, the treatment  was discovered by accident, and we are not sure exactly how it works.

We know short wavelengths of infrared  light, known as near infrared, interact with specific enzymes inside our  cells, triggering some chain reactions. Some of these reactions kick up  energy production in our cells, and that boost of energy could help our  cells protect themselves and repair damage. These interactions also produce  bursts of reactive oxygen species, unstable molecules that can interact  easily with other molecules.

Reactive oxygen species are mostly  known for just wreaking havoc in the body, but they also play an important role in interacting with  the molecules that regulate our immune response. So, triggering these bursts may help keep  inflammation from getting out of hand. These chain reactions kicked off by infrared light may also help protect against  neurodegenerative disease.

Experiments in mice and rats  with traumatic brain injuries have also shown that near infrared light triggers the growth of new brain cells and  new connections between cells. It’s not clear yet how true this is  for humans, but it’s at least a hint that our windows may be depriving us of  some real benefits of infrared light. Not in my case though, because I  don't have windows in my office!

So, what do we do about the fact  that many of us are stuck inside for most of the day, behind windows that  filter out a bunch of natural daylight? Some people have argued that we need  to scrap windows with low-e coatings. The problem is … they do a lot of good.

One federal report found that they can cut  buildings’ HVAC costs by almost a third. So getting rid of them isn’t a great answer. And so far, we don’t have any great answers.

But that’s not to say there’s nothing we can do. Some people have tried using artificial lights to mimic natural daylight cycles  and help sync our body clocks. And these days, there are modern windows  that essentially work like transition lenses, adjusting their filters in real time.

Could those be tweaked to let in more  daylight at certain times of the day, like mornings and evenings,  when the Sun isn’t so hot? Or… going forward, maybe we could design buildings that are more naturally  suited to their environments. Instead of filling city centers  with boxy glass buildings that need constant climate control,  we could take some lessons from older, local architecture, which at least  has windows you can open to let a breeze in.

I’m not saying this is easy. Engineering solutions for our  modern lives will be complicated, especially when it comes to managing  something like the Sun’s radiation, which does both harm and good. So it’s going to take some real creativity.

But in the meantime, we should  do our best to get outside and soak up some unfiltered  daylight whenever we can. That’s the real answer for me. And I hope I can do it.

This video was inspired by The Inner  Clock, a new book by Lynne Peeples. It’s all about circadian rhythms, and the  surprising number of ways they affect our lives. I really enjoyed it.

If you’d like to check it out,  head to the SciShow Bookshop page. It’s a thing that we have now. That’s exciting for me.

This video was made possible by  the Alfred P. Sloan Foundation. [♪ OUTRO]