For optimal energy efficiency, it is desirable to minimize air leaks though the exterior walls of the house. Good indoor air quality, however, requires adequate ventilation with outside air. Indoor air pollution can be caused by exhaust from appliances, dust, and animal dander. An Energy Recovery Ventilator (ERV) allows us to maintain superior air quality in the house while minimizing energy losses.

ERVs operate by exchanging stale, interior air for fresh, outdoor air. In the winter, the stale indoor air is generally warmer and more humid than the fresh outdoor air (which is generally TOO dry for comfort). The ERV transfers heat and humidity from the stale air being exhausted to the incoming outdoor. This transfer is 95% efficient. As a result, less energy is required to heat and humidify the fresh air. 

In the summer, of course, the opposite is true and the ERV works to reduce the temperature and humidity of the incoming fresh air.

ERVs are installed in line with a home's normal heating and air conditioning system, and can be placed at any location in the system. Fresh air intakes and an exhaust must also be installed in the home's exterior, and are usually 6 to 8 inch round openings. ERVs use very little energy because their only moving parts are a fan that moves the air across the heat exchanger.

The 2005 Maryland house featured a Stirling Technologies UltimateAir RecoupAerator 200DX ERV. This unit is the most energy-efficient and best-performing ERV available on the market.

More information on ERVs is available from The Home Ventilating Institute (HVI) website. HVI is the non-profit association that represented the manufacturers of home ventilating products. This organization offers a wide variety of services, including standardized tests for currently marketed ERV units, furnaces, and air conditioners.