Have you seen a car ad on television that shows the noisy chaos of the world outside the car before it pans to the driver inside the quiet, luxurious interior of said car, protected from the elements outside? The message you’re supposed to take from this juxtaposition is that this car is “tight”—sealed off from the world outside and all its perils.
This sealing up is done for a few reasons: it provides a quiet interior, for sure, and it makes your air-conditioning and heating more efficient because the car is less “leaky.” But it also comes with an unexpected side effect: the pollutants inside the car have nowhere to go, leading to a buildup of potentially toxic pollutants emitted from materials inside the car, and a buildup of carbon dioxide emitted from the car’s occupants. We regularly see levels of CO2 inside cars that are as much as four to five times higher than what we allow in buildings. Ever get sleepy while on a long drive with the family or friends? The high carbon dioxide levels in your car are contributing to that—it’s one of the reasons you’ve likely heard the recommendation to roll down your windows if you feel sleepy while driving.
Buildings are the same. Like humans, they need to breathe. But, as with cars, we’ve done one hell of a job over the past 40 years of cutting off their air supply.
For over a hundred years, there have been efforts to figure out the proper amount of fresh air that needs to be brought into a building. Beginning around the time of the energy crisis in the late 1970s, we did our best to tighten our building envelopes and reduce ventilation rates in an effort to conserve energy. The goal for our homes and offices and schools was to make them less leaky.
We were very successful in these efforts. Kudos to the energy engineer pioneers in the 1970s for helping to alleviate the energy crisis in buildings. But maybe they should’ve consulted some health scientists along the way. The result of sealing up our buildings, as you likely guessed from the car story: a buildup of pollutants indoors. And with it, the birth of a phenomenon known as Sick Building Syndrome. So there you have it—if you don’t feel well in a building, you can thank a set of energy engineers who decided that the best way to tackle the energy crisis was to choke off your air supply.
Studies have found that in North America and Europe, we spend 90% of our time indoors. Some jobs have you out and about more, and kids tend to spend a little more time outside than adults—but for most of the developed world, it’s more accurate than you might think. (In some places and in some seasons, that 90% is actually an underestimate; in the United Arab Emirates, it can be more like 99.9% indoors for some people.)
To put this 90% figure in perspective, it’s useful to think of what it means in terms of our own lives. By the time we hit 40, most of us have spent 36 years indoors. Try it for yourself: take your age and multiply it by 0.9. That’s your indoor age. If we are lucky enough to live to 80, most of us will have spent 72 years inside! When we look at it this way, in terms of years, it becomes obvious and intuitive that our indoor environment would have a disproportionate impact on our health.
Sometimes we think that all we really need to do to advance the Healthy Buildings movement is mention this 90% fact. After hearing that, how could anyone conclude that the indoor environment does not impact our health? Heck, we spend a third of our lifetimes in one little box on this planet—our bedrooms!
Here’s a weird but helpful way to think about all of this indoor time, courtesy of Rich Corsi, dean of engineering and computer science at Portland State University: “Americans spend more time inside buildings than some whale species spend underwater.”
What?! It’s kind of hard to wrap your head around this—that whales spend more time on the surface than we, as land mammals, spend outdoors—but it’s true. We would never go about trying to understand whales by studying the air they breathe when they are at the surface; we study them where they live, underwater.
And yet that’s exactly what we do with humans. For all this time spent indoors, we tend to focus much more on outdoor air quality than on indoor air quality. Check any newspaper or news site on any given day and you are likely to see a story about the hazards of outdoor pollution, but how often do you see a story about building health?
Our regulatory system is also geared toward the outdoor environment. In the United States, we have the Clean Air Act, but what about a “National Indoor Air Quality Standard”? No such thing. The only things akin to this in the United States are the legally enforceable limits set by the Occupational Health and Safety Administration for exposures to pollutants indoors. But very few scientists, if any, would argue that the OSHA limits are truly protective of health.
What most people don’t fully recognize is the extent to which outdoor air pollution can penetrate inside a home or building. As you might expect, there are a lot of factors that determine just how much outdoor air pollution enters a building, or what we call infiltration factors. Things like the year of construction and leakiness of the building, whether there are operable windows (and whether they open or not), and the type of ventilation and filtration system in your building are the obvious ones, but wind direction, pressure, and other meteorological factors also play a critical role.
Every single day, you can find a news story somewhere about how bad outdoor air pollution is in places like Mexico City, Seoul, New Delhi, or Beijing—and it truly can be bad, dangerously so. That news story is typically accompanied by a picture of a parent and young child walking hand in hand outside with dust masks over their noses and mouths, engulfed in a haze of air pollution. But we challenge you to find a news story that talks about what happens when that parent and child go inside. You will never find this “dirty secret of outdoor air pollution” in the news. We look forward to the day when a news story about outdoor air pollution is accompanied by a picture of a family sitting on the couch wearing dust masks. (A public health side note to readers: those paper dust masks don’t actually work against this type of pollution; they’d have to be on their couch wearing an N95 mask.)
In addition to outdoor air pollution penetrating indoors, we also have indoor sources of air pollution. After we trapped ourselves in these airtight chambers and became appalled at the odors we started to notice, we started to use sprays, candles, and scented cleaners to make that stuffy indoor air smell just a bit better, without realizing that those sprays can create a whole other set of attacks on our health. And then we doused ourselves in underarm deodorant, cologne, perfume, and scented shampoo so we would smell good in all of these stuffy boxes we created. Not to mention all the building materials and furniture that off-gas pollutants into our sealed-box homes and offices. There are all sorts of potential indoor contaminants, some of which you may be familiar with, and some of which you probably haven’t thought much about.
With this assault on our health, you might be forgiven for thinking that all is lost and you should spend the rest of your life living in the mountains or in a hermetically sealed bubble. That’s not necessary. There is good news here: Your building can actually help mitigate the impact of this assault. There’s a massive opportunity in front of us when we begin to shift from thinking about green buildings, which largely focuses on the 1% of costs associated with energy, waste, and water, to thinking about Healthy Buildings, which focuses on the 90% of the costs of our buildings—the people.
This article was excerpted with permission from Healthy Buildings: How Indoor Spaces Drive Performance and Productivity (Harvard University Press, 2020).
Joseph G. Allen is director of the Healthy Buildings Program and an assistant professor at Harvard’s T. H. Chan School of Public Health. Allen is serving as cochair of the International Well Building Institute’s Coronavirus Task Force. John D. Macomber is a senior lecturer in Finance at Harvard Business School. His work focuses on the future of cities, particularly as aided by the private finance and delivery of public infrastructure projects in both the developed and emerging worlds.