ERV and HRV (balanced ventilation)

Tight, efficient buildings need deliberate ventilation for good air quality. Balanced systems exhaust stale air and supply an equal amount of fresh air, passing both streams through a heat-exchanger core. A heat recovery ventilator (HRV) transfers heat; an energy recovery ventilator (ERV) also transfers some moisture, which helps in humid summers and very dry winters.

Residential ventilation rates in the US are commonly based on ASHRAE Standard 62.2. Controls can modulate ventilation from CO₂, humidity or occupancy sensing and coordinate with the main HVAC system.

Where it bites: filters need regular maintenance, unbalanced or undersized systems underperform, cold climates need frost protection, and integration with the main HVAC controls is often an afterthought.