HRV and ERV

A heat recovery ventilator and an energy recovery ventilator both exhaust stale indoor air and supply fresh outdoor air through a core that transfers energy between the two streams, so ventilation does not throw away all the conditioning.

Tight construction no longer ventilates itself. Without deliberate ventilation, moisture, carbon dioxide, cooking and cleaning products and other contaminants accumulate. Balanced ventilation supplies and exhausts roughly equal amounts, avoiding the pressure imbalance that exhaust only ventilation creates.

1. 1Two fans move air in opposite directions through a single unit.
2. 2The streams pass through a core, separated so they do not mix in a properly functioning unit.
3. 3Energy transfers through the core walls between outgoing and incoming air.
4. 4In cold weather a defrost mode periodically recirculates or pauses to clear frost from the core.
5. 5A control sets continuous, intermittent or demand based operation.

• Never balanced at commissioning, so the unit pressurizes or depressurizes the building.
• Filters and core left unmaintained, cutting airflow.
• Exterior hoods blocked by screens, snow or debris.
• Condensate drain plugged or trapped incorrectly.
• Defrost failing in cold weather, icing the core.
• Ducting to the wrong locations, so stale air is drawn from the wrong rooms.

Required ventilation rates, duct configurations, commissioning and balancing documentation vary by jurisdiction, adopted code edition and the manufacturer instructions.