North Americans spend as much as 90 percent of their time indoors. Whether at home, work or play, our time is increasingly spent inside buildings. Since we always need air to breathe, we should make every eff ort to protect the quality of that air. On any given day, we each consume more air than we do water or food, both of which are highly regulated for safety. As a society, we spend large sums of money to guarantee our food and water supplies meet rigorous quality standards. Regulating the quality of our indoor air may be more challenging, but it is clear there is a direct correlation between ventilation and indoor air quality (IAQ). Decades of study of IAQ have led to the development of industry-recognized ventilation rates, which are intended to maintain reasonable air quality.
Health Consequences
The U.S. Environmental Protection Agency (EPA) has determined that indoor pollutants can be two to five times higher than outside air pollutants. Poor air quality contributes to asthma, respiratory infections, allergic reactions, headaches, eye and skin irritations, fatigue, dizziness and nausea. Studies suggest a person’s ability to perform mental tasks requiring concentration, calculation or memory can be negatively impacted by air quality deficiencies.
Some health issues may be evident following limited exposure to “bad air”. Other health impacts may only appear after long and repeated exposure to contaminants, which is even more reason to make certain the best possible indoor air quality is provided and maintained.
In addition, uncontrolled indoor moisture levels can result in mold growth and damage to fi nishes and structures. Mold is a signifi cant problem in housing, and good ventilation is one of the solutions to ensure that damp conditions necessary for growth are controlled.
Sources of Pollution and Control
Our homes are often fi nished with materials containing a wide variety and complexity of chemicals. Paint, cabinets and fl oor coverings all can contain chemicals that contribute to poor indoor air quality. We fill our homes with furnishings, electronic equipment, cosmetics and cleaning products that add to the contamination of the air we breathe. It has become a common but ill-advised practice to use plug-in air fresheners and other odor-masking sprays to temporarily hide unpleasant odors, which only adds more chemicals to the living environment.
So what can we do to remedy the problems associated with poor indoor air quality? First, we can exercise care when we select the materials used to finish the interiors of our homes. Today, homeowners can select paint, fl oor coverings, cabinets and other finishing materials that have very low levels of volatile chemicals. It is somewhat more di fficult to control the furnishings and electronics, but we can minimize the use of cleaning products and select those that are environmentally preferable. And good ventilation practice can replace the need for chemical-based air fresheners.
Ventilation – Natural Is Not Enough
Ventilation – simply exhausting stale indoor air and replacing it with fresh outside air – is one of the best ways to ensure continuous indoor air quality. However, su fficient exchange of air without mechanical assistance is generally just not possible. Older homes certainly have more air leakage than those built in recent years, but the problem is that those leaks do not guarantee stale air will be replaced by fresh air. In new homes, air leakage is minimized through the use of improved building practices, more e fficient windows and air tightness testing. Th e benefi ts are lower heating and cooling costs and the opportunity to apply mechanical ventilation to give homeowners greater control over their environment.
Intermittent Ventilation
Bathrooms need mechanical ventilation to exhaust moisture from bathing and odors. Moisture not properly managed can create conditions for mold to grow, creating health concerns and damaging expensive-to-repair finishes. It is best to exhaust moisture directly from showers. HVI-Certif ied ventilation products rated for installation in showers are readily available.
Kitchens also require mechanical ventilation to address the odors and moisture created from cooking. A properly sized and ducted range hood located over the cooktop will ensure contaminants are exhausted directly to the outside. Very large capacity range hoods actually need outside air to be supplied to compensate for the air being exhausted. Make-up air systems linking the operation of the hood to an inlet device are necessary to ensure that the house is not depressurized. Depressurization may cause backdrafting of combustion appliances such as furnaces, boilers and hot water tanks. More information on selecting range hoods can be found on the HVI Web site.
Additional rooms used for crafts or hobbies that produce air contaminants need to be separately ventilated to ensure the contaminants do not mix with the general house air.
Continuous Ventilation
While some specifi c areas of the home need local, intermittent ventilation to manage obvious IAQ issues, the entire house needs continuous ventilation to help ensure general air quality is maintained in all areas. Th ere are several strategies that can be used to meet this need.
Surface-mounted fans designed for quiet, continuous operation can be installed in a central area of the home to meet the ventilation requirements stipulated by the local building authorities. Some ventilation systems now utilize “smart” technology, linking separate fans to address both intermittent and continuous needs.
Heat and energy recovery ventilation systems have the added benefi t of saving energy and distribution of tempered fresh air to bedrooms and other living areas. In some cases, HRVs and ERVs can be used to provide both continuous and intermittent ventilation using switches in bathrooms that increase the ventilation rate for short periods of time.
HVI-Certi fied Ventilation Performance
Indoor air quality control through mechanical ventilation is a key component of all well-equipped residential dwellings and a necessity for those meeting green building standards. When selecting residential ventilation equipment, look for the HVI-Certified label; your assurance the product has been independently tested for air flow, sound and energy performance. To verify that certifi ed performance is maintained, the products are independently retested according to a regular schedule by HVI.
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