An Energy Recovery Ventilator (ERV) provides controlled fresh air ventilation while transferring both heat (sensible energy) and moisture (latent energy) between incoming and outgoing air streams. This dual transfer makes ERVs more effective than HRVs in climates where humidity control is important.
In summer, an ERV pre-cools and pre-dehumidifies incoming outdoor air using the cooler, drier indoor exhaust air — reducing both the temperature and humidity that the air conditioner must address. In winter, it both warms and humidifies incoming air using exhaust air.
ERVs are the preferred choice in mixed and humid climates (most of the southern, southeastern, and Pacific Northwest US). They are also appropriate in climates where maintaining indoor humidity in winter (rather than reducing it) is important. ERV cores are typically made of a moisture-permeable membrane that allows water vapor but not gases to transfer between air streams.