A bathroom fan exhausts stale air. An HRV exhausts stale air and recovers heat. An ERV does the same and also transfers moisture. All three move air. Only two save energy. Only one is right for your specific climate and home.
The three devices, defined
Exhaust fan. A one-way fan that blows indoor air outside. Bathroom fans, range hoods, simple whole-house exhaust fans. No heat recovery. Cheap to install, cheap to run, effective in small doses.
Heat recovery ventilator (HRV). A balanced system. Equal parts fresh outdoor air in, stale indoor air out. A heat exchanger core transfers sensible heat (temperature) between the two airstreams without mixing them. Typical efficiency: 70 to 85%.
Energy recovery ventilator (ERV). Same as HRV, plus the exchanger transfers moisture (latent heat) between the airstreams. Keeps humid summer air from dumping water vapor into your home. Keeps dry winter air from stealing your humidity.
Pick the right one for your climate
When a fan is enough
Small spaces, mild climates, intermittent needs. A bathroom fan running 20 minutes after a shower does exactly what it needs to. A vented range hood does the same for cooking. You’re willing to lose the conditioned air because the alternative (residual moisture, cooking byproducts) is worse.
ASHRAE 62.2 allows fan-based whole-house ventilation in some configurations, usually paired with a calculated run schedule. Cheapest path to code compliance.
When HRV wins
Cold and dry. Northern U.S. winters, Canada, Scandinavia, mountain West. Heating bill is substantial, outdoor air is already dry, you don’t need to transfer moisture between airstreams. The HRV recovers 70 to 85% of the heat you’d otherwise throw out with the stale air.
HRVs also win when indoor humidity needs to stay low for building-science reasons. Tight homes with moisture-sensitive assemblies. An ERV in that context would slow the humidity drop, which you don’t want.
When ERV wins
Humid climates and most U.S. homes. Summer in the Southeast, coastal Pacific Northwest, Gulf Coast, anywhere outdoor air is sticky. An HRV would push that humidity into the house. An ERV catches most of it on the exhaust side and sends it back out. Same logic in winter in dry climates: ERV keeps your indoor humidity from collapsing to 15%.
Rule of thumb: cooling season longer or more energy-intensive than heating? ERV. Winter dominates the bill? HRV.
Capacity matching
ASHRAE 62.2 sets the whole-building rate around 7.5 L/s per person plus 1 L/s per 10 m² of floor area. In traditional units, that’s roughly 0.01 CFM per square foot plus 7.5 CFM per occupant.
For a 2,000 sq ft home with 4 occupants: 20 + 30 = 50 CFM continuous. You can size an HRV/ERV to deliver that steadily, or go bigger with a smart controller that boosts on demand.
How Vyana fits
Most HRV/ERV retrofits assume central ducted distribution: runs of dedicated ductwork to every room, a central unit in the basement or attic. That’s a serious renovation. Vyana takes a different architecture. An intake unit near the existing HVAC return register, an exhaust unit at the far end of the house. The HVAC fan distributes the fresh air through ducts that are already there. No new ductwork. The system can boost ventilation at night when occupants are home and dial back during the day, which is where most of the energy savings come from.
Frequently asked questions
Which is better for a cold climate, HRV or ERV?
In a cold, dry climate (interior continental), HRV usually wins because you don’t want to conserve indoor moisture. In a cold but humid climate (coastal Northeast winters), ERV usually wins.
Do I need an HRV/ERV if my house is already leaky?
Technically no. Practically yes. Envelope-leak ventilation is uncontrolled: over-ventilates on windy days, under-ventilates on calm days, no heat recovery. An HRV/ERV lets you tighten the envelope and add controlled, recovered ventilation.
What’s the typical CFM for a 2,000 sq ft home?
Per ASHRAE 62.2: roughly 50 CFM continuous for 4 occupants. Boost capacity for kitchens and bathrooms adds another 100 to 150 CFM during active periods.
Can I install an HRV myself?
A central ducted HRV/ERV is a two-day pro job. Through-wall units like Vyana are designed for self-install: cut a hole, mount the unit, plug it in. An afternoon.