COVID19 has put a spotlight on indoor air quality (IAQ), and homeowners are looking for ways to improve the health of their interior environments. I recommend the following as an actionable, cost-effective plan for improving IAQ in single-family homes.
Part 1: Evaluate the existing conditions
A home is a system of systems, meaning everything is connected. The goal is to reduce the potential for harmful feedback loops, such as tightening the building enclosure without upgrading the ventilation system.
People are a part of the system of systems. People are the main source of carbon dioxide (CO2) in a building. If CO2 is high, it means other pollutants along with infectious viruses and bacteria are also building up. This can occur where people gather and can be exacerbated by tight buildings without good ventilation.
Outdoor and indoor air
Outdoor air pollutants can concentrate inside. This can happen if your home is tight or leaky. Outdoor air quality is defined and measured by the Environmental Protection Agency (EPA) but indoor air, where we spend 90% of our time, is not. It’s up to you to identify the sources of indoor-generated pollutants.
Radon is the second leading cause of lung cancer. It is a radioactive soil gas and, depending on the radon zone you are in, can be present inside your home. There is no way to know without measuring.
Open-combustion appliances or equipment that uses fossil gases or solid fuel include cook stoves, water heaters, and furnaces with “open vents,” ventless fireplaces and wood stoves. All can release a wide range of indoor air pollutants. If carbon monoxide (CO) is present, it is likely several other pollutants are also present. Use CO as a proxy for combustion appliance–related bad air. Such equipment also emits surprisingly large amounts of particulate matter.
Unconditioned attached garages, basements/crawlspaces, and attics often communicate with conditioned spaces. When there are unsealed openings between these areas, polluted air can make its way into the living spaces. Think: dust, mold or other biologicals, water vapor, and exhaust fumes.
Sources of chemicals
Disinfectants, cleaning agents, cosmetics, lotions, paints/stains, and like products, as well as new furnishings and items that off-gas when new can combine to form other dangerous chemicals that pollute the air. Many such chemicals can also interact with chemicals on our skin.
Part 2: Set priorities and take action
Here is a list of 11 priority areas with advice on addressing them and the associated costs:
Priority 1: Know outdoor air quality to control indoor air quality
Priority 2: Use open-combustion appliances wisely (and infrequently, if possible)
Priority 3: Control radon
Priority 4: Monitor CO
Priority 5: Exhaust cooking gases
Priority 6: Exhaust water vapor
Priority 7: Monitor CO2
Priority 8: Reduce air leakage
Priority 9: Minimize exposure to chemicals
Priority 10: Filter indoor air
Priority 11: Get an energy audit
I consider these areas to be the low-hanging fruit when it comes to improving IAQ. In general, they are listed in order of what to consider and act on first, second, third, etc. to ensure an orderly and consistent approach. It approximates the order I would use as a building scientist when doing an energy audit, but at a client-friendly “DIY-but-do-no-harm” level. For an energy or home performance audit, I would do a deeper dive and get more into the math and physics; I would also use blower-door, infrared, and various other testing equipment. My hope here is to demonstrate that you don’t necessarily need to invest in an entirely new HVAC system to better your indoor environment.
Monica Rokicki is a BPI Analyst, Healthy Home Evaluator, and founder/CEO of Better Building Works LLC in Roanoke, Virginia.
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