You can see dust and smell smoke. Most indoor air pollutants give no sign at all. According to the EPA, Americans spend about 90% of their time indoors, where some pollutants are often two to five times more concentrated than outside. For most families, the air at home is the air they breathe most.

Here is where indoor air pollution comes from, and what a well-built home does about it.

Where indoor air pollution comes from

  • Everyday activities. Cooking, especially frying and gas burners, releases fine particles and gases. Cleaning products, air fresheners and candles add more.
  • Materials and furnishings. New paint, flooring, cabinets and furniture release volatile organic compounds (VOCs), most heavily in the first months. A 2016 analysis in Environmental Science & Technology found 45 potentially harmful chemicals in U.S. household dust, 10 of them in at least 90% of samples.
  • Moisture. Showers, cooking and breathing all add moisture. In a damp Pacific Northwest winter, too much of it leads to condensation, mold and dust mites.
  • Radon. This colorless, odorless gas comes up from the soil. The EPA estimates radon causes about 21,000 lung cancer deaths a year in the U.S., making it the second leading cause after smoking. Oregon Health Authority test data rates large parts of north, northeast and southeast Portland as high risk.
  • Wildfire smoke. Late-summer smoke is now a regular part of life in the Portland and Vancouver area, and fine smoke particles get into any home that leaks air.

What a well-built home does about it

Controls air leaks

A leaky home pulls in air from wherever it can: the crawlspace, the garage, the attic. An airtight home lets you decide where the air comes from and filter it on the way in. That’s why we measure air leakage with a blower door test on every home.

Supplies fresh air on purpose

Once a home is tight, ventilation has to be designed in. An energy recovery ventilator (ERV) supplies a steady flow of filtered outdoor air and exhausts stale air from kitchens and bathrooms, recovering most of the heat in the process. Marnella homes use a Broan ERV with the Virtuo air monitoring system, which watches air quality and humidity and adjusts ventilation automatically. The design details matter. We cover the common errors in ventilation mistakes that sabotage healthy homes and ventilation mistakes in Portland net-zero homes.

Keeps humidity in range

The EPA recommends indoor humidity between 30% and 50%. Balanced ventilation does most of this work, and a monitoring system shows you when levels drift.

Filters what comes in

For wildfire smoke, the EPA recommends a MERV 13 filter in central systems that can handle it, and running the fan more often while smoke lasts. Keeping ducts inside the insulated part of the home also stops the system pulling dusty air from the attic or crawlspace.

Plans for radon

The only way to know your radon level is to test. Building in a radon system during construction costs far less than adding one later, and it can be activated if a test comes back high.

Starts with cleaner materials

Choosing low-emission paints, adhesives and cabinetry reduces the chemical load from the start, and ventilation clears what is left. Healthy-home certifications such as Wellness Within Your Walls check these choices independently.

Keep it working

Replace HVAC and ERV filters on the schedule the manufacturer sets, and more often during smoke season. Have the system inspected every year. We also recommend having the ducting cleaned every five years.

What to ask when you build or buy

Ask how the home is ventilated, whether air leakage and ventilation airflow were tested, and where the ducts run. A builder who designs for indoor air will have clear answers and test results to show you. All of this starts at the design and planning stage. For the bigger picture of air, water and light together, read The Wellness-Centric and Eco-friendly Home.

Sources: EPA, indoor air quality · Mitro et al., Environmental Science & Technology, 2016 · EPA, radon · Oregon Health Authority, radon by zip code · EPA, mold and moisture · EPA, wildfire smoke