Energy recovery ventilation
Energy recovery ventilation (ERV) is the energy recovery process in residential and commercial HVAC systems that exchanges the energy contained in normally exhausted air of a building or conditioned space, using it to treat (precondition) the incoming outdoor ventilation air. The specific equipment involved may be called an Energy Recovery Ventilator, also commonly referred to simply as an ERV. During the warmer seasons, an ERV system pre-cools and de-humidifies the intake air; during cooler seasons the system humidifies and pre-heats the incoming air. The exchange of humidity across the intake and exhaust airflows is the main differentiating factor in how an ERV operates as compared to a standard residential heat recovery ventilator (HRV), which does not allow the transfer of humidity between the airstreams. An ERV system helps HVAC systems design meet ventilation and energy standards (e.g., ASHRAE), improves indoor air quality, and reduces total HVAC equipment loads, thereby reducing energy consumption. ERV systems enable an HVAC system to maintain a 40-50% indoor relative humidity, essentially in all conditions. ERV's must use power for a blower to overcome the pressure drop in the system, hence incurring a slight energy demand. Nearly half of global energy is used in buildings, and half of heating/cooling cost is caused by ventilation when it is done by the "open window" method according to the regulations. Secondly, energy generation and grid is made to meet the peak demand of power. To use proper ventilation; recovery is a cost-efficient, sustainable and quick way to reduce global energy consumption and give better indoor air quality (IAQ) and protect buildings, and environment. An ERV is a type of air-to-air heat exchanger that transfers sensible heat as well as latent heat. Because both temperature and moisture are transferred, ERVs are described as total enthalpic devices. In contrast, a heat recovery ventilator (HRV) can only transfer sensible heat. HRVs can be considered sensible only devices because they only exchange sensible heat.