I worked for a number of years, like many people, in an office building with windows that did not open. For the first time in my life, a slight soreness tingled in my throat almost every day. Each time a denizen of that floor got a cold, it decimated at least a third of the floor’s employees. For the next week or two, a swath of cubicles would sit empty. I took to avoiding pressing the water cooler button with a bare hand.

For the sake of energy efficiency, more and more buildings are sealed off completely to the outside world, relying on mechanical ventilation for airflow. But little science has been done to explain how our architectural choices are changing the world of microbes that live inside these buildings—and human health. If I wanted to test whether it was really my office getting me sick (or figure out strategies to avoid it), I wouldn’t have much to go on.

But that’s about to change: The National Academies of Sciences has spent the better part of the year gathering scientists, architects, and engineers to understand the indoor microbiome, which will culminate in a review paper released at the beginning of next year. The National Academies hopes the paper will serve as a guidepost for future research, by nailing down which unanswered questions about the indoor microbiome are most critical to society.

The stakes are high: Americans spend almost 90 percent of their time indoors, so almost all of our microbial exposure occurs inside buildings. That entire time, we’re being enveloped by millions of organisms we can’t see. That’s because a building, like a human gut or vagina, has a microbiome too—a community of microbes that live and thrive in it. Only about 20 percent of the microbes in any given occupied building come from the humans inside, according to Yale University professor and chemical engineer Jordan Peccia, who studies how microbes move inside rooms and through vents (he helped write the National Academies study). “When you come into your home, or your office, you’re completely and continually bathed in those microbes,” Peccia says.

We don’t yet know exactly how our architecture and design choices are influencing them—we just know they absolutely are influencing them. We’re already unintentionally choosing to live with certain organisms and to keep others out just by deciding how a building will be heated and cooled, or how it will be occupied. “Those decisions affect the microbial ecology of a building,” he says. “Now we’re trying to build a framework so we can start to model buildings and say: This design will lead to this type of microbial ecology.”

Tightening up

Already a question that has drummed up a lot of attention from the group is the issue of building “tightness,” or how the sealed windows in my office might have been affecting my health.

Scientists already know that children who are more exposed to microbes from the outside world—especially from animals—have lower rates of immune problems and of diseases like asthma. Bavarian farm children who grew up in close contact with animals, for example, had drastically lower rates of asthma and allergies. And in Northern Canada, Inuit children’s asthma-related health problems plummeted after ventilation systems were installed in their homes, where windows had always been sealed to retain heat.

Peccia’s own studies have tried to answer the question of what kinds of outdoor microbes appear to be good for kids. He tracked children from the time they are in utero to see whether certain microbes in their house might contribute to a diagnosis of asthma in early childhood. But instead, he says, “we found no microorganism that seemed to cause asthma, or to protect them from asthma. But what had a strong protection was diversity. If they were exposed to a diverse array of fungi and microbes, they were less likely to get asthma.”

So what happens when buildings in our modern, hyperclean society get tightened even further?

Back in the 1970s, right after the first energy crisis, architects began sealing up buildings for the sake of energy efficiency—adding insulation, thickening walls, making windows less permeable. Around the same time, doctors began seeing patients with a mysterious constellation of symptoms—cough, chest pain, shortness of breath—that went away almost as soon as they left the buildings they worked in. Now, architects are well acquainted with that illness, which they call sick building syndrome. It’s become a cautionary tale of how not to design a building: With insufficient ventilation, any toxic or irritating fumes from 1970s formaldehyde-laden building materials would offgas and stay put, for inhabitants to breathe in.

Since then, new regulations have limited the noxious fumes in paint and flooring, but architecture is entering a new era of building “tightness” as cities try to take on climate change, says Robin Geunther, a principal architect at Perkins + Will who designs hospitals, and who is also involved in the National Academies study. “Our desire to save energy, and our desire to live sustainably, is in some instances driving us to more tightly sealed, mechanically ventilated buildings,” she says.

Antimicrobial architecture

Not only are buildings become more sealed off, but Geunther is worried about a trend she is seeing in hospital design: Companies are beginning to advertise antimicrobial paints and flooring. In the world of hospitals, that might be a very enticing add-on: The potential for catching an infection is highest inside a hospital, and those infections are much more likely to be fatal.

At the same moment as the FDA recently banned antimicrobials like triclosan from hand soap, Geunther is seeing it sold as an additive in building supplies without any proof that they actually reduce infectious diseases. “Building products don’t have any disclosure requirements, or any oversight. Unsubstantiated product claims are rampant and becoming more rampant in the building industry,” Geunther says. Already, researchers behind a study of buildings where antimicrobials like triclosan are being used found antibiotic-resistant genes living in the microbes in the buildings’ dust. “Since antibacterials have been linked to more resistant bacteria, why would we put that in our hospitals?”

Americans today are living in a massive real-time microbial experiment. Two generations ago, people lived in much “looser” buildings, where indoor and outdoor air was continually exchanged. Plus, building materials used to be much more natural—now they’re predominantly synthetic, which means the dust we breathe is man-made. Beneficial indoor bacteria might eat those synthetic compounds, or they might not—and if they do, are they being altered by toxic effects? “Is the flame retardant in building materials having the same endocrine disrupting effects on them as they do on us? How are they adapting to this?”

Geunther hopes the National Academies study will start to prod at some of these questions, but for now, she says, “It’s a good a sci fi plot, isn’t it?” It’ll be a long time before I know if the sealed windows in my old office were to blame for the floor-wide sick days. But for now I’ll stick to not touching the water cooler.