What Is a Heat Recovery Ventilator (HRV)?
An HRV is a ventilation device that exhausts stale indoor air and brings in fresh outdoor air while transferring heat between the two streams — recovering 60-90% of the exhaust energy that would otherwise be wasted. It is the standard ventilation solution for tight, energy-efficient buildings where natural infiltration no longer provides fresh air. ERVs (energy recovery ventilators) add moisture transfer for humid climates.
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HRV vs. ERV
HRVs transfer sensible heat only (temperature); ERVs transfer sensible heat plus moisture (latent). In cold dry climates, HRVs are ideal — they keep indoor humidity from dropping further. In hot humid climates, ERVs are preferred — they pre-dehumidify incoming air, reducing the cooling load. The MEP engineer selects based on climate zone and building use; the distinction matters for both energy modeling and comfort.
Where they are used
High-performance homes (Passive House requires heat recovery ventilation), schools, offices, and multifamily — anywhere the envelope is tight enough that exhaust-only ventilation would depressurize the building. Commercial DOAS systems incorporate the same heat-recovery principle at larger scale with enthalpy wheels. Code-required ventilation rates (ASHRAE 62.1/62.2) are what the HRV delivers; the recovery is the efficiency bonus.
Sizing and installation notes
Size from the ventilation rate calculation, not from rules of thumb — oversized units short-cycle and waste energy. Ductwork must be sealed and balanced; an unbalanced HRV pressurizes or depressurizes the house, driving moisture into walls. Filters need regular replacement (the number-one maintenance failure), and in cold climates the unit needs a defrost strategy. Commission the airflow — rated recovery means nothing if the ducts leak.
The bottom line
HRVs recover 60-90% of exhaust heat while ventilating tight buildings; ERVs add moisture recovery for humid climates. Size from ventilation calculations, seal and balance ducts, and maintain filters.
Torch Engineering PLLC · (480) 490-0064 · info@torchengineering.com — PE stamping backed by Apex Grid Engineering.