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I sat down with Kevin Kennedy, an environmental public health scientist and nationally recognized expert on healthy homes, to learn about indoor air quality (IAQ) and what homeowners can do to improve it — especially during cold and flu season. This is our conversation, which has been edited for length and clarity.

Kevin, thanks so much for speaking with me. You have 30 years of experience working on healthy housing, and your current title is "environmental hygienist.” Can you explain what that means?

Sure. I currently work with Children’s Mercy Kansas City hospital. In this role, I integrate my background in buildings and environmental science with my passion for children's health. I helped develop the environmental health program that allows us to go into homes, schools, childcare centers — any place where children live, learn, and play — to assess the indoor environment and guide families or staff in making improvements. Over the years, we have received grants and foundation funding to support our work, and we also do research in the home environmental health field.

Let’s start with the basics now: How do you define a healthy home?

Fundamentally, it's about protecting the people who live in the home. I use the "8 Principles of Healthy Homes” to define it as a home that is:

  • Clean

  • Dry

  • Pest-free

  • Contaminant-free

  • Safe

  • Ventilated

  • Comfortable

  • Maintained

The definition that the surgeon general provided some 12 years ago is a good starting point: Healthy housing is designed, constructed, operated, and maintained in a way that promotes good human health.

But that definition, and our knowledge, have evolved, thanks to ongoing scientific research. We know so much more now about the “microbiome” in homes, comprising good microbes and the bad ones we call “germs.” At the same time, we’re more aware of the thousands of chemicals (including cleaners and disinfectants) that people are exposed to in their homes. All these things are interrelated.

So indoor air quality, which is our focus today, is only one aspect of a healthy home?

Correct. A healthy home takes into account all the ways we interact with our indoor environments, including the air we breathe. What we’re breathing influences allergies, asthma, and so many other health issues. People are paying more attention than ever to indoor air due to the pandemic. Good indoor air quality is closely related to those 8 Principles of Healthy Homes. The EPA is a great resource to learn more about indoor air quality and potential health effects.

Big picture, how do we start improving our homes’ indoor air quality?

At a basic level, it's about controlling what you're exposed to within your home, primarily chemicals and breathable particles. Chemicals could be from outside air pollution that have come in through windows, doors, or gaps in your building enclosure, or from, say, cleaners, paint, or coatings on your furniture. Particles like dust floating in the air can also originate from inside or outside. Aerosols that contain COVID-19 or flu germs, like water droplets, have a tendency to attach themselves to other particles in the air, which allows them to be distributed even farther.

It’s easiest to start improving by adopting cleaning strategies that don't use harsh chemicals. You can use vinegar and water. You can dust more frequently, but with a damp cloth, so you reduce the amount of chemicals and particles. Then you make sure the equipment or home systems are in place to capture and remove what is still present.

So there are simple, practical actions we can all take to improve indoor air quality. But we need our homes to help us out, too. What do those systems look like?

The same home features that improve energy efficiency and comfort, like proper air sealing and caulking, also tightly control where air can flow into your home. That enables you to use a mechanical ventilation system, such as Heat Recovery or Energy Recovery Ventilation (HRV or ERV, respectively), which funnels outside air in at a specific point to run it through a filter before directing it through your home. That filtered air passes through sealed ductwork, so it doesn’t leak out and dust and dirt can’t get in. Zonal controls for the ventilation system determine where and how often air is distributed through the home. Research shows that these kinds of home systems significantly improve the indoor environment and what people are exposed to.

The average home, however, doesn't have those kinds of systems or support, so you don't have control over what you’re exposed to. There isn’t a dedicated source of fresh air; instead, it comes in through leaks and gaps. Your HVAC system is just sort of throwing air around in your house. If the filter isn’t highly efficient, the same pollutants can just get recirculated.

How does moisture in your home fit into this?

Research shows that chronically damp homes, and the resulting microbial agents, are very bad for people's health. There’s a misconception that if just one room is constantly damp, it won’t affect the rest of the house. But if your basement stays damp, that damp air — potentially carrying bad, moisture-loving microbes or mold spores — ultimately gets distributed to other parts of the house. I recommend everybody get a cheap temperature/humidity gauge to move around the house to understand where your problem areas are. Generally, you want 30–60% relative humidity.

For controlling moisture across the entire house, air conditioning systems can be effective, but people typically don’t leave them on long enough at a time to remove enough moisture. The AC system should be on for at least 20 minutes for effective moisture removal from the air. The ERV mechanical ventilation systems I mentioned earlier can also be very effective at helping control humidity throughout your home. And, of course, there are room dehumidifiers you can place in specific problem areas. There are a lot of factors about the home and its location that have to be considered, so it’s a good idea to work with a professional to evaluate what’s best for your particular home.

As the weather cools down (at least in my little corner of the world), flu season is ramping up. What are some practical ways people can improve their indoor air quality overall and hopefully reduce their chances of spreading infections?

In addition to what I’ve already talked about, regular maintenance for your heating, cooling, and ventilation (HVAC) system is important. Have a professional regularly inspect and service it to make sure it’s running properly and there are no leaks. Have your ducts inspected and cleaned, if needed, to remove mold, mildew, or particles building up inside.

You can also add an in-room air filtration unit to reduce aerosol particles overall. I’m not talking about the electronic or ionic varieties, often called air purifiers. In real-world applications, they aren’t nearly as effective as basic filtration for reducing airborne viruses. If your HVAC system is compatible with higher-efficiency filters with a Minimum Efficiency Reporting Value (MERV) rating of 12 or above, install those. Researchers found that good high-efficiency particulate air (HEPA) filtration and good quality in-room air filtration units are very effective at helping reduce the aerosol transmission of COVID. It makes sense that they will also help with other airborne particles and microbes. So if you used any of these filtration methods during the pandemic, don’t stop!

How do you know if you need to take more drastic measures to improve indoor air quality?

That's tricky. Some people will feel like smaller steps are good enough. I see many people who have chronic health issues, seasonal allergies, and autoimmune disorders making bigger investments in their home’s systems or design because the indoor environment plays a role in how they feel.

The right trained professional, whether a contractor or home inspector, can help you determine if you need to air seal your home, seal your ductwork, or make larger upgrades like installing a new ventilation system. By the “right trained professional,” I mean someone who has had additional training and knowledge of the 8 Healthy Home Principles or indoor environmental health science.

Ultimately, the best thing is a combination: changing behaviors and changing home systems. It all works together to promote health, with the added benefit of increasing energy efficiency.

Ready to start following Kevin’s advice? Pearl Certification is here to help. Our Green Door app is designed to help you make smart decisions about your home, including upgrades related to indoor air quality. Sign up to get customized recommendations to help you meet your goals. Through the app, you can also connect with high-quality contractors in your area to discuss potential upgrades.


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