Energy Recovery Ventilation Systems

Energy Recovery Ventilation Systems

An energy-recovery ventilator (ERV) is a type of mechanical equipment that features a heat exchanger combined with a ventilation system which provides controlled ventilation into a home or building while minimizing energy loss. An exchange process occurs within the unit between cool air being pulled into the system and warm air being exhausted. The heat from the exhausting air is used to warm the cool fresh outside air closer to room temperature therefore saving on heating energy costs.

Most Energy-Recovery ventilation systems can recover about 70%–80% of the energy. The systems are most productive though in the winter months so they are best suited for areas with extreme winters or summers, and where fuel costs are high. In mild climates, the cost of the additional electricity consumed by the system fans may exceed the energy savings from not having to condition the supply air.

Remember that using energy that is not needed can account for as much as 50% of your energy bill. It is advisable to perform a home energy audit with a system such as Step by step Home Energy Audits.

These systems are also equipped to remove or add humidity depending on the moisture level of the air being brought in from the exterior. With an Energy Recovery ventilator, the heat exchanger transfers a certain amount of water vapor along with heat energy, while a heat-recovery ventilator only transfers heat. Since an energy-recovery ventilator transfers some moisture from the exhaust air less humid incoming winter air, the humidity of the house air stays more constant. This also keeps the heat exchanger core warmer, minimizing problems with freezing.

In the summer months the energy-recovery units work best in conjunction with an air conditioning system. The system can be set to run only when the air conditioning operates or all of the time. The most cost effective method and the best for air quality is running in conjunction with an air conditioning unit. Units can also be equipped with a moisture sensor so that if the air coming in is to humid the system will shut down to avoid raising humidity inside the home or building. If you live in areas of hot humid summers it is advisable to only run with the air conditioning and equip your system with the humidity sensor option.


Energy Recovery ventilation systems require more maintenance than other ventilation systems. They need to be cleaned regularly to prevent deterioration of ventilation rates and heat recovery, and to prevent mold and bacteria on heat exchanger surfaces. The cleaning of the units is crucial to avoid health issues with mold or mildew. If a house is constructed tighter than 0.5 air changes per hour, any pollutants generated in the home can accumulate and reduce the indoor air quality to unhealthful levels. If fresh outside air is brought in through an open window to alleviate this problem, this air may be excessively hot, cold or humidity-laden and require conditioning at added expense. So the energy-recovery units can be the best choice for many climate areas to provide proper air flow as long as the units are properly operated and maintained.

If you choose to use an energy-recovery system the normal locations for supply and return ducts is the living area and each bedroom. Keep the duct runs short as possible and properly sized for optimal ventilation and energy cost. Insulating of the ductwork is advisable to maintain the air temperature inside the duct.

Since the objective of theses systems is the energy efficient operation of your ventilation system you may also want to install a Solar Attic Fan which compliments the operation of a Energy Recovery system.

If you are installing your own system make sure you research the units and choose a reliable energy efficient model properly sized for your home. In addition obtain all necessary permits and inspections. If your choice is a professional installer then always get:

1. A copy of Bond and License 2. A calculation sheet on sizing of system 3. A copy of type, model and make of equipment and its warranty. 4. A first year maintenance contract 5. References for work on energy recovery systems

Make sure to check with the Better Business Bureau for any issues.

Keys to the proper choice:

1. The climate of your area 2. The Humidity levels in the summer months 3. Energy Costs in your area 4. The cost of installation on older homes

If energy costs are high in your area the Energy Recovery system is probably a very wise choice for reducing your costs. You may also want to consider some or all of the following alternative energy systems:

Green Power
3. Solar Water Heating