Home Renovation Best Practices for Protecting and Improving Indoor Air Quality

by Rachel White

From COVID to cooking contaminants, when learning about a new (or not so new) indoor air hazard, it’s easy to either overreact or underreact — to worry that our buildings are slowly killing us, or to shrug our shoulders and dismiss the hazard, assuming there’s not much we can do about it anyway. The truth is that while the indoor air quality (IAQ) in most buildings, including our homes, is not horrible, it often could be much better. And there are things we can do to make it better, particularly when renovating.

Just as a home renovation often provides opportunities to improve comfort and efficiency, it also often provides opportunities to improve IAQ. At Byggmeister we strongly advocate for seizing these opportunities whenever feasible. Conversely, renovations can worsen IAQ, at least temporarily, by introducing construction-generated contaminants, which means we also need to protect workers and occupants from pollutants during our projects.

Here are five strategies we employ at Byggmeister to protect and improve IAQ on our projects.

Strategy #1: Assess Existing IAQ Issues

Whenever we start a new project, we assess the home for existing IAQ issues:

• First, in our new client questionnaire, we ask homeowners whether they have any air quality concerns and if anyone in their household has health conditions that may be exacerbated by indoor air pollutants.
• Second, we look for and document visible contaminants, such as friable asbestos and mold, and test for contaminants such as radon and combustion gases that can’t be seen.
• Third, we test existing bath fans and kitchen hood vents to determine how much air they are removing from the house. We also ask the homeowners whether they use these systems and if not, why not.

Once we have determined where we can make improvements, we incorporate remediation as appropriate into our scope. One of the most common IAQ improvement measures on our projects — which also happens to be a key decarbonization measure — is to replace existing gas appliances with electric ones. Many of our clients are highly motivated to switch to induction cooking, even if they aren’t otherwise renovating their kitchen, because of the links between gas cooking and indoor air pollution.

Strategy #2: Use Healthy Materials

Building materials have historically been a significant source of indoor air pollution — from formaldehyde in pressed wood products to solvents and heavy metals in oil-based paints. The good news is that within the past several years, healthier products have become more widely available, as have resources to help find them.

These resources include product guidance provided by organizations such as the Healthy Building Network; product certifications; and lists of chemicals of concern such as the Living Building Challenge Red List.

Some of the steps we have taken to use healthier materials include giving preference to water-based floor finish and low-VOC and no-VOC paint; limiting our use of spray foam to applications where there is no other option; using vinyl flooring sparingly; and when we do use it, specifying products with minimal off-gassing.

There is certainly more that we could be doing. The truth is, it’s hard to consistently select materials that we know for sure won’t compromise IAQ. Information about what’s in products is harder to find than we would like. And switching out products takes time — time to identify alternatives, to understand trade-offs, and to build consensus around the change.

Reducing indoor air pollution from building materials is an ongoing challenge that we’re committed to tackling — which is why over the course of this year our design team has made it a priority to review and update our specifications to ensure that we are using healthier materials.

Strategy #3: Protect Workers and Occupants

Even when we use healthier materials, renovation work inevitably introduces some indoor air pollutants. Demolition and construction are dusty, and sometimes the least toxic product still contains chemicals of concern. To protect workers and occupants from unavoidable indoor air pollutants we:

• Maintain dust walls with zippered doors to separate work areas;
• Run negative air machines to ventilate work areas;
• Ensure that occupants stay out of the work areas and that workers wear proper personal protection when indoor air pollutants are generated.

Occasionally, occupants may need or want to vacate the house entirely. For example, when we install spray foam (which we do sparingly because of its high upfront carbon and toxicity), installers need to wear personal protective equipment, and occupants need to leave during installation and remain out for at least 24 hours afterwards. During this time, we also ventilate continuously.

Strategy #4 Improve Airtightness

Contrary to popular belief, leakier houses do not necessarily have better IAQ than tighter homes. In fact, when outdoor air quality is compromised — whether from wildfire smoke, vehicle exhaust, or construction work —IAQ may be worse in a leakier house than a tighter house.

Even when outdoor air quality is good, leaky envelopes aren’t a reliable source of fresh air. “Natural” air exchange between outdoors and indoors is driven by weather conditions, so sometimes you’ll get too much and sometimes you’ll get too little. In the colder months dry outdoor air is pulled in, and in the warmer months hot humid air pushes its way in, which makes controlling indoor temperature and humidity difficult. Moreover, building envelope flaws are often in dirty places such as at the mud sill on top of the foundation and around windows. That’s why best practice is to build (or renovate) tight and ventilate right.

Strategy #5 Install Effective Ventilation

Both tight and leaky homes can have poor IAQ if they don’t also have effective ventilation. Until recently it was thought that exhaust only kitchen and bathroom vents could serve as effective ventilation in both leaky and tight homes.

Over the past decade studies have shown high levels of indoor pollutants in homes with exhaust-only ventilation and substantially improved IAQ when balanced ventilation is installed. While properly installed and consistently operated exhaust ventilation can effectively remove moisture and point source pollutants caused by bathing and cooking, it doesn’t do a good job of improving air quality elsewhere in the home.

This is why balanced ventilation such as an Energy Recovery Ventilator — which steadily supplies filtered outdoor air to bedrooms and living spaces and steadily exhausts stale air from bathrooms — is now considered the gold standard. And while continuous exhaust-only ventilation is still allowed in many places, as of January 2023, balanced ventilation is required under the Stretch Energy Code for new homes in Massachusetts.

So, what does this mean for our projects? First, we want to make sure that existing bath and kitchen exhaust vents are working properly. If not, we want to fix or replace them. Second, we advocate for incorporating balanced ventilation when we have relatively easy access to space for ductwork. Because it can be challenging and costly to run ductwork throughout an entire house that isn’t being fully gutted, we often propose balanced ventilation just for the bedrooms because we spend a lot of time in our bedrooms, and many of us sleep with our doors and windows closed, which can contribute to the build-up of pollutants.

Photo: Energy Recovery Ventilator

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And what about if you aren’t renovating? You can use your hood vent and run your bath fan on a timer so that it continues to run after you leave the room. When you use products that contain chemicals of concern you can use them outdoors or in well-ventilated spaces. And you can swap out the products you use for healthier alternatives. Lastly, you can decide now that when you do undertake that substantial renovation, you’ll make IAQ a priority — just as you would efficiency and comfort.