Some homeowners wonder if their homes could be making them sick. Is the air in their homes unhealthy? Could it be contributing to family illnesses?
In fact, indoor air quality ranks as one of the top five environmental health risks. Indoor air is commonly more polluted than outdoor air. The Environmental Protection Agency reports that indoor levels of pollutants are commonly at least two to five times higher than outdoor levels.
As homes become tighter, allowing less air infiltration, indoor air quality issues can occur. If not enough fresh air is entering the home, concentrations of numerous pollutants can reach unhealthy levels.
Air quality challenges
Moisture issues and mold growth Many homes have high moisture levels in the basement, bathrooms, attic, and other areas of the living space. Common causes are water penetrating into the home or elevated moisture levels from occupant activities, including showering and cooking.
This high moisture level can allow mold growth and create a breeding ground for bacteria and dust mites. Mold-associated illnesses can cause fatigue, difficulty concentrating, stiff joints, headaches, and sinus congestion, while dust is a common allergy and asthma trigger.
Although it may seem that there is limited airflow between the basement or crawlspace and the living spaces of a house—this often isn’t the case. In many homes the air quality in the basement or crawlspace has a large impact on the air quality on the first floor.
Ineffective exhaust fans Many homes rely on exhaust fans to remove cooking fumes, excess moisture, and odors. For exhaust fans to work properly, equal amounts of air must enter and be extracted from the home. Homes that have been air-sealed have fewer leaks where air can infiltrate. In these homes bathroom and kitchen exhaust fans may not operate correctly because the home is too airtight.
In other homes, exhaust fans do not properly vent to the outside. Instead, they may exhaust the humid air into the attic, where it can create a moisture issue in another part of the home.
Off-gassing from building products and furniture More than 80,000 chemicals are used in everyday commerce, and few of these have been thoroughly studied. A variety of chemicals are found in carpeting, furniture, building products, and even personal care products. Many home items contain formaldehyde, benzene, ammonia, toluene, and other chemicals. When homes are poorly ventilated, pollutants become trapped indoors.
Lack of fresh air Many homes do not have enough fresh air coming in to dilute pollutants. Also, instead of controlling where air enters the home, many houses allow air to seep in through the walls, crawlspace, garage, and basement. This can allow dust, mold, automobile exhaust, and other chemical pollutants to enter the living spaces. These pollutants become more concentrated during colder weather when the windows are closed.
Combustion gases Atmospheric hot water heaters and some gas furnaces may not adequately vent carbon monoxide gases out of the home. This is especially common in airtight homes, because atmospheric hot water heaters rely on makeup air from air leaks to remove gases. Common signs of improper venting of a hot water heater include melted plastic and rust on the top of the unit. If a hot water heater shows signs of improper venting, it should be replaced with a different type.
Healthy Air Solutions
Although indoor air quality may seem like a daunting topic, there are many effective solutions for promoting healthy indoor air in the home. Most of the strategies fall into two categories: preventing pollutants at the source and diluting or removing them with proper ventilation.
Control moisture To prevent mold growth, healthy homes do not have elevated moisture levels. Any unaddressed water leaks or points of moisture penetration must be remedied. Moisture should be controlled in all areas of the home, including the basement and crawlspace,map to prevent mold growth. When exhaust fans are used, they must vent properly to the outside of the home, and sufficient quantities of makeup air must be able to enter so that these systems will operate properly.
Whole-house ventilation systems, such as Zehnder heat recovery ventilation (HRV) systems and energy recovery ventilation (ERV) systems, provide a comprehensive ventilation strategy for the home. These systems both supply fresh air and remove stale air from the home, for balanced ventilation. HRV and ERV systems can replace exhaust fans in the bathroom and kitchen, successfully extracting moisture even in more airtight homes.
Supply fresh air Effective in diluting the level of pollutants, fresh air is essential in the home. Depending on the climate, opening windows can be an effective strategy for part of the year if pollen and other airborne pollutants aren’t an issue. HRV and ERV systems bring a constant supply of fresh air into the home throughout the year, while removing stale air from the kitchen and bathroom.
Remove pollutants Filtering the air in the home with a fine filter helps reduce pollen, pet dander, dust mites, and other pollutants. Some homes have whole-house air filtration systems that do this. Furnaces also have filters that can help clean indoor air as it cycles through the home, if the proper filters are used and changed periodically. The intake air in Zehnder HRV and ERV systems is filtered to help remove contaminants, with finer filters available to remove smaller particles.