The one-way approach to mechanical ventilation has been updated for the 21st century into a balanced, whole-house approach. HRV and ERV ventilation systems induct fresh, filtered outdoor air into the house while exhausting stale, polluted indoor air at exactly the same rate. Utilizing small-diameter dedicated ductwork or your existing HVAC ducts if preferred, along with a central unit that incorporates intake and exhaust fans plus a heat exchanger, these systems run continuously at a selectable speed and rate of air exchange.

Stale indoor air is removed from areas like the kitchen and laundry room while an equal volume of fresh outdoor air is delivered to bedrooms and living areas. Because the exhaust and intake volumes are balanced, indoor air pressure remains neutral, not depressurized as with conventional exhaust ventilation.Efficient heat recovery ventilation is key, allowing for a good indoor air quality and saving energy. In Passive House, at least 75% of the heat from the exhaust air is transferred to the fresh air again by means of a heat exchanger.