Heat-Recovery Ventilation (HRV/ERV)
CSI Division 23, HVAC
Mechanical ventilation equipment that captures heat, and in some units moisture, from the air being exhausted out of a building and uses it to pre-warm or pre-cool the fresh air being brought in, rather than simply exhausting that energy to the outside.
Why it matters
A tightly sealed, energy-efficient building still needs fresh air brought in continuously, but bringing in untreated outside air would waste much of the energy savings the tight envelope was built to achieve. Heat-recovery ventilation is what lets a building get fresh air without giving up most of that efficiency, which is why it's central to standards like Passive House.
On a real project
A Passive House project installs an energy-recovery ventilator that captures heat and humidity from stale indoor air being exhausted and transfers it to the incoming fresh air stream, maintaining comfortable, efficient ventilation without the energy loss untreated outside air would otherwise cause.
Who this matters most to
An HVAC Technician installs and balances heat-recovery ventilation equipment, a different system from a standard furnace or air handler, since its entire purpose is energy recovery rather than simply heating or cooling air.
Where this goes wrong
A tightly sealed, energy-efficient building is ventilated with a standard exhaust fan system instead of heat-recovery ventilation, since the two look similar on paper. The building ends up losing much of the energy efficiency its tight envelope was designed to achieve, since all that conditioned air's energy simply vents straight outside.