Energy Recovery Ventilator (ERV)
From Swikipedia
Introduction
An Energy Recovery Ventilator (ERV) is a mechanical device that draws stale air from the house and transfers the heat or coolness in that air, to the air being pulled into the house. This can help reduce energy costs and dilute indoor pollutants.
Brief Description
ERVs are especially recommended in climates where cooling loads place strong demands on HVAC (heating, ventilation and air-conditioning) systems. However, keep in mind that ERVs are not dehumidifiers. They transfer moisture from the humid air stream (incoming outdoor air in the summer) to the exhaust air stream. But, the desiccant wheels used in many ERVs become saturated fairly quickly and the moisture transfer mechanism becomes less effective with successive hot, humid periods. In some cases, ERVs may be suitable in climates with very cold winters. If indoor relative humidity tends to be too low, what available moisture there is in the indoor exhaust air stream, is transferred to incoming outdoor air.
ERVs also allow the exchange of moisture to control humidity. This can be especially valuable in situations where problems may be created by extreme differences in interior and exterior moisture levels. For instance in cold, heating-dominated climates, better air flow and the introduction of humidity to the indoor environment can help control wintertime window condensation. In humid summer climates which are cooling dominated, it can be critical to dry out incoming air so that mildew or mold does not develop in ductwork.
After passing through the heat exchanger, the warmed or cooled fresh air goes through the HVAC air handler, or may be sent directly to various rooms. Stale air from return ducts pre-conditions the incoming flow before exiting. Systems in various sizes and configurations are available to automatically maintain 0.35 air changes per hour, the rate usually recommended to maintain good air quality. Many systems include filters to further control contaminants that would otherwise re-circulate through the home.
The benefit of using energy recovery is the ability to meet the ASHRAE ventilation & energy standards, while improving indoor air quality, and reducing total HVAC equipment capacity.
References:
http://www.greenbuildingcookbook.info/Glossary.html
http://www.toolbase.org/Technology-Inventory/HVAC/energy-recovery-ventilators
