Using Natural Light with care…

We’re used to thinking that natural light is magical, something we can’t get too much of—it elevates our mood (for more on reasons to design to encourage good moods, read this article) and makes sure our brain is purring along in tip top fashion. Daylighting boosts our mental and physical wellbeing and performance—but, like most things in life even the bestiest best stuff can’t be used recklessly.

Things to think about as you design that new home with only glass walls or truck your curtains to Goodwill are:

• Temperature. In many parts of the world, lots and lots of natural light in a space can mean lots of heat in an area (if windows are not insulated it can mean lots of low temperatures also). When temperatures are not what we find pleasant we are stressed and when we’re stressed we’re distracted from whatever we’re up to, whether that’s writing a report for work or needlepointing or trying to get children to stop fighting. When stressed we also don’t get along as well with others as we do when we’re not feeling tense. Also, when we’re hot our perceptions of whatever physical environment we’re in will fall; for example, we’ll feel more crowded when hot than when not. You can use surface colors to alter how warm or cold it seems in a space, at least to some extent. A truly hot space will seem hot no matter what color you paint the walls—but, if you think the situation is salvageable: areas featuring cooler colors will seem slightly cooler and those where warmer colors predominate slightly warmer (this effect can result in perceived differences of 5 degrees Fahrenheit). If you’re going to have lots of daylight in a space, make sure that you get out all of your fans and maybe even turn on the air conditioner some, even if the daylight space isn’t actually too warm—when a space has more natural light in it people will feel it’s at least slightly warmer than if it’s missing all of those rays of sunlight.

• Glare. Things can get glare-y when there’s lots of natural light if, for example, shiny surfaces abound or our angle to the window is not just right so we have trouble reading the screens on our devices, for example. When we are experiencing glare, we get tense which, as mentioned earlier is definitely not a good thing. There is also some evidence indicating that facing into sun so intense we start to frown, which often happens with glare, may make us more aggressive. And, just to complicate things: when it’s hot we think there’s more glare.

• Privacy. When glass windows are large or positioned just wrong, and people will be moving by outside, those passersby can look inside if sight blocking curtains/blinds aren’t in place. And when windows are big, those curtains/blinds can get expensive. Most of the time this doesn’t matter a great deal—if you’re like most people you probably don’t spend nearly enough time romping around your house naked, at least from the perspective of voyeuristic neighbors. But not having privacy means that you lack some control over your at-home experiences—even if you’re not romping, you like to think that you could at any time—and missing out on reasonable opportunities for control makes us wary and causes us to feel at least a little unsettled.

But just because daylight can complicate our lives, don’t cut it out. Satish, Joseph, and Nanavati (2022) report that “Exposure to daylight, in particular, plays an outsized role in our overall well-being and mental health. Like almost all animals, humans have a circadian cycle that regulates sleep, metabolism, heart rate, and body temperature over a 24-hour cycle. Daylight is the main environmental stimulus that syncs the body’s internal clock with the external world. . . . Studies have shown that daylight access can reduce stress, lower blood pressure, and even improve a person’s cognitive function” (Usha Satish, Anjali Joseph, and Kaushal Nanavati. 2022. “Illuminating Results,” Healthcare Design, vol. 22, no. 2, pp. 26-27).