Sick buildings: the unseen health threat during winter months

As winter sets in, most of us instinctively prepare our bodies to fend off seasonal illness—avoiding those with flu symptoms, layering up on colder days, and stocking up on immune boosters. But while we’re doing everything to protect ourselves, we often overlook one key factor in our well-being: the buildings in which we spend most of our time.

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Yes, buildings can get sick too.

Wynand Deyzel, commercial air-treatment expert at Solenco, warns that poor indoor air quality, especially in office buildings, hospitals and care homes, can significantly contribute to illness, particularly in the colder months. “Sick buildings are real,” says Deyzel. “And it all starts with the air we breathe indoors—where we spend over 86% of our time.”

Deyzel says that a lack of proper ventilation is a common culprit. “Poorly ventilated spaces lead to both high levels of carbon dioxide, and a build-up of Volatile Organic Compounds (VOCs) released by cleaning chemicals, printers, and office furniture which can cause everything from eye irritation, nausea and headaches to decreased cognitive function and long-term health risks,” he says.

But moreover, Deyzel says that this lack of ventilation combined with air-conditioning systems creates extremely low humidity levels that pose a real threat to our health.

A growing body of research backs this up. In a recent webinar hosted by Harvard Medical School and ASHRAE, Stephanie Taylor—a physician and architect—highlighted the alarming connection between low indoor humidity and increased infection rates.

Deyzel notes, “a quote shared during that session really stuck with me: ‘We shape our buildings – and then they kill us.’ That’s from Dickerman of Harvard Medical School, and it couldn’t be more relevant today.”

Humidity saves lives

Taylor’s extensive seven-year study of hospitals and elderly care homes found that maintaining indoor humidity between 40–60% relative humidity (RH) significantly reduced infection rates. In fact, during the Covid-19 pandemic, buildings that kept humidity within this range saw fewer fatalities.

“Low humidity impairs our mucosal immune system,” Deyzel explains. “It allows viruses and bacteria to travel further and survive longer. When RH drops below 40%, our natural defenses are compromised, making us more vulnerable to airborne infections."

And while this insight is particularly relevant to healthcare environments, Deyzel stresses that it applies equally to everyday spaces like workplaces and homes. “Any building that doesn’t control its humidity levels can become a sick building, increasing the risk of illness among its occupants.”

It’s here where understanding how to manage your air, including the role of humidifiers to restore dry indoor air to optimal RH levels becomes critical.

“Balanced humidity isn’t just about comfort,” says Deyzel. “It’s about well-being, immune support, and even productivity. You can’t fix what you don’t measure, which is why monitoring indoor air parameters like temperature, humidity, CO₂ levels, and volatile organic compounds is crucial.”

The implications extend beyond individual health. Healthy air is good business. Improved indoor air quality leads to fewer sick days, greater cognitive function, and higher workplace productivity.

Deyzel concludes: “Indoor climate control can no longer be considered a luxury. It’s a public-health issue and a wise investment. We prioritise sleep, nutrition, and exercise—now it’s time we treat the air we breathe with the same importance.”