What Is an Air Exchanger?

Air Exchangers Improve Indoor Air Quality

• In older homes built during times of low energy costs, outdoor air replaced indoor air every 30 to 40 minutes. In tightly constructed homes, it takes 10 hours for air exchange to take place. An air exchanger improves indoor air quality by regularly exchanging and filtering outdoor and indoor air. In doing so, air exchangers reduce the levels of airborne chemicals, gases and particles. Chemicals come from building materials, upholstery, cleaning and personal care products, hobbies and cooking. Gases come from older gas-burning furnaces and appliances, which can leak and produce carbon dioxide and carbon monoxide from incomplete combustion. Human metabolic processes also produce carbon dioxide, ammonia, organic substances and odors. Particles such as pet dander, tobacco smoke and dust contribute to poor indoor air quality and related health issues such as colds, allergies and lung disease.

Cost of Air Exchangers

• Consumers can expect to pay from $500 to more than $2,000 for an air exchanger in 2011, with installation costs of $500 or more. When considering a purchase, examine other factors such as cleaning ease and frequency, sensors to turn the unit on and off, and defrosting features. A 2009 calculation by North Dakota State University for a three-bedroom home heated with fuel oil --- factoring in energy cost, number of heating degree days, number of home occupants, square footage and other factors --- indicated that the air exchanger would pay for itself in roughly three years, three months. According to NDSU, an air exchanger increases resale value and protects the structure of the home.

How Air Exchangers Work

• During the winter, an air-to-air exchanger moves indoor and outdoor air through a filtration system that vents pollutants while transferring heat from the outgoing warm air to the incoming cool air. During the summer and in warm climates, the process works in reverse, removing outdoor heat and humidity before filtered air enters the home. Although homes in colder climates typically have "heat recovery ventilators" designed to retain heat without reducing humidity, some homes in all climates have "energy recovery ventilators" to remove both heat and humidity.

Efficiency

• Because manufacturers use varying specifications when providing efficiency information, the Home Ventilating Institute performs tests on air exchangers and provides standardized criteria for comparing systems. Consumers should look at the energy performance "sensible recovery efficiency" when comparing systems. For maximum impact, air exchangers should circulate air into all rooms of the home, including the attic and basement, and have several points of air intake and exit. Typical installations have the exchange equipment located in the basement or attic.