“Ask an Expert” with Kris Knutson

Winter weather has finally arrived and we are spending more time indoors.  What can we do to improve indoor air quality?

Good indoor air quality (IAQ) is important regardless of the time of year.  The EPA estimates that  “on average, Americans spend about 90  percent or more of their time indoors” and that “indoor levels of pollutants may be two to  five times higher, and occasionally more than 100 times higher, than outdoor levels.”  Poor IAQ has been connected to attention deficit disorder and asthma in children. Although IAQ is a complex subject, these four simple, core principles can help guide your thinking: elimination, reduction, ventilation and filtration.

I will address the four core principles in a 3 part series. In this first part, I’ll talk about elimination and reduction.

Eliminate – Start with Common Sources
Elimination of pollutants is the keystone of quality indoor air.  This means removing substances from the home which are known to be detrimental.

Start with things that can be easily eliminated by changing your behavior.  Candles (petroleum or plant based), incense, indoor smoking, and kerosene or propane space heaters are common sources of indoor pollution.  They all introduce a variety of harmful substances into the air, including carbon monoxide and other combustion gasses, and particulate matter, which can lead to respiratory illness, skin irritation or even death.

(Candles and Incense as Potential Sources of Indoor Air Pollution: Market Analysis and Literature)

Instead of burning incense, eliminate sources of foul odor, like emptying a litter box or compost bucket regularly.  Ventilating the room with outdoor air is also highly effective, and is the subject of part two of this series.  If you still want to add fragrance, consider thinly slicing an orange on a plate, or if you burn incense, light it for only a few seconds and then extinguish completely.  Simmering spices has been a traditional remedy for covering odors, but this introduces excess moisture into your home and should be avoided.

Instead of burning candles, eliminate the pollution by not using them, or use a battery powered LED candle or a colored LED or CFL bulb.

Cabinets with low levels of formaldehyde.

Next, take a look at the materials in your home. Formaldehyde is one of the most common and harmful substances found in composite wood products commonly used in cabinets, shelving, etc.  In new construction, sources of formaldehyde can be eliminated through careful selection of framing materials, built-in cabinets and shelving.  For existing homes, replacement materials such as trim or cabinets and furniture should be selected based on low formaldehyde levels.  In both cases, look for hard wood products or composite products complying with California Air Resources Board (CARB) Airborne Toxic Control Measure (ATCM) Phase II requirements for lowest emissions.

Finally, avoid “room vented/venting” or “flue-less” heating appliances, as they vent combustion gasses into the room.  When adding a room heater, install a direct vent fireplace or wood stove with a Canadian Standards Association rating of at least 60 %.  This ensures efficient operation and that exhaust gasses will be immediately vented outdoors.  Electric space heaters are an attractive option, but can cause large increases in electric bills.  Also, generators should never be run indoors, in basements or in attached garages.  They should be run out of the home and away from operable doors or windows.
Once major sources like these have been eliminated, reduce the level of remaining pollutants.

Reduce pollutants – Complete a Radon Test and Make Retrofits

The U.S. Surgeon General, the EPA and Build It Green recommend that all homes, both new and existing, be tested for radon.  Radon is an invisible, odorless, naturally occurring radioactive gas that comes from decaying soil and rock in the earth’s crust and can get trapped inside homes.  It is the second leading cause of lung cancer in the United States of America behind tobacco smoking.  There is no safe level of radon in a home, but your risk for illness is highly variable, varying from house to house and person to person.

Measure radon levels in your home by completing a radon home test kit, available at hardware, home improvement and online stores.  The one-time test calls for opening a small packet, leaving it in your home for a number of days, and sending it to a test lab.  These test kits, including the lab results, cost approximately $25.  Constant monitoring with an alarm can be done with a digital device, which costs about $150.  Knowing the radon level in your home, and considering other risks will help you decide if you need to consider a retrofit of your home to reduce exposure.  Retrofitting for Radon safety typically includes adding a vapor barrier to a crawlspace, sealing cracks in basements and installing a vent pipe.

Learn more about radon safety and mitigation.


Navigating the complexities of IAQ can be challenging, but by educating yourself and hiring a home performance contractor you can do something about the health of your home.  Home performance contractors specialize in whole-house solutions to improve air quality and comfort, reduce energy bills, intrusion of soil and combustion gasses, and unwanted odors.  At the same time they can give you an overview of the safety, comfort, health, durability and energy efficiency of your home.

Home performance contractor performing a blower door test.

Energy Upgrade California helps you find home performance contractors qualified to assess your home and make upgrades and offers up to $4,000+ in rebates to help cover the cost.  See a list of participating home performance contractors in your area and incentives at www.energyupgradeca.org

In part two, I will discuss ventilation.

For more information on these and other best practices, visit the free Build It Green fact sheet library.

Kris Knutson is a former Home Performance Contractor and consultant, and current Program Associate with Build It Green.  He manages the Ask an Expert Hotline, which provides California residents customized responses to green building questions for building professionals and the general public.  Submit a question!

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