Energy-recovery Ventilators: Ventilate Your Home with Minimal Energy Loss

Enlarge Image Image Gallery An energy-recovery ventilator provides fresh indoor air and helps control humidity levels while conserving energy. KEITH WARD

Sealing air leaks and adding insulation are two important ways of conserving energy in your house. But some homes may be so tightly sealed that they don’t allow in enough fresh air for a healthy environment. To allow adequate fresh air into your house (without using extra energy to heat or cool the fresh air) you might need some type of ventilation system. Energy-recovery ventilators, also known as air heat exchangers, are mechanical ventilation systems that remove stale, polluted air from homes and replace it with fresh outdoor air.

To conserve energy, energy-recovery ventilators pass the outgoing warm air from inside the house through an internal component called a heat exchanger. In the heat exchanger, heat from the outgoing air is transferred to the cool incoming air. This exchange (heat recovery) prevents the home’s occupants from being blasted with cold winter air. It also saves considerable energy because the home’s heater doesn’t need to warm the cold incoming air. In the summer, outgoing room air cools the incoming warm air, helping to maintain comfort.

Energy-recovery ventilators can be operated by timers or controlled by humidistats, sensors that detect humidity levels in a home. Energy-recovery ventilators often remove excess humidity, but also can be set to add humidity. They cost about $500 to $1,700 (see “What Will It Cost?”, below).

When researching energy-recovery ventilators for purchase, don’t be confused by the terminology. An energy-recovery ventilator is not the same as a heat-recovery ventilator. In an energy-recovery ventilator, the heat exchanger transfers a certain amount of water vapor — along with heat energy — to the incoming air. A heat-recovery ventilator transfers only heat. Because an energy-recovery ventilator transfers some of the moisture contained in the exhaust air to the usually less humid incoming winter air, the humidity of homes with energy-recovery ventilators tends to stay more constant. This feature also keeps the heat exchanger core warmer, minimizing problems with freezing.

Installing an Energy-recovery Ventilator

Although you can purchase a small wall- or window-mounted energy-recovery ventilator, most are large units that are suspended from the ceiling — usually in attics, utility rooms, basements or crawl spaces.

Installation is a job for a professional. Energy-recovery ventilators require two connections to the outdoors — one to exhaust stale indoor air and the other to bring in fresh outside air. According to the Sustainable Building Sourcebook, “The inlet and outlet on the building exterior need to be distanced from each other to avoid cross-contamination.” Ideally, they should be located on different sides of the house.