Tight buildings save energy and trap their own air. Heat-recovery ventilation resolves the conflict: it keeps fresh air flowing while keeping most of the paid-for energy inside. This guide explains how HRV and ERV units differ, which climates each suits, and what the fan inside contributes.
What heat-recovery ventilation does
Both HRV (heat-recovery ventilator) and ERV (energy-recovery ventilator) units contain the same three things: a heat-exchanger core, fans, and controls. Exhaust air from wet rooms and fresh outdoor air pass through the core side by side, never mixing, and the exchanger moves heat — or coolth — from one stream to the other. The outgoing air pre-conditions the incoming air, so the ventilation keeps running while the energy largely stays in the building. Indoor air quality improves and energy consumption drops substantially at the same time.
HRV: recovering sensible heat
In an HRV, the core transfers heat only. Warm extract air gives up its temperature to the cold supply air in winter; in summer, the flow reverses its benefit and pre-cools incoming air. What it does not transfer is moisture: the water vapour in the extract stream leaves the building with the exhaust.
ERV: recovering heat and moisture
An ERV goes one step further. Its exchanger transfers heat together with a share of the water vapour, so moisture migrates between the airstreams instead of being dumped outside. In winter, humid indoor air loses less of its moisture to a dry outdoor supply; in summer and in humid weather, a muggy outdoor stream passes part of its load to the drier exhaust. The result is a more even indoor humidity level on top of the heat recovery.
Which unit fits which climate
The working split is straightforward:
- HRV usually suits colder climates with long heating seasons, where the priority is holding on to heat and the outdoor air is dry.
- ERV is the better fit for warmer, humid climates with long cooling seasons, where refusing to import outdoor moisture is worth as much as refusing to export cooled air.
Neither is universally better; the climate decides, and many buildings in between the extremes choose either based on their dominant season.
The fan inside the unit: EC dual-inlet impellers
The heat exchanger gets the attention, but the fans decide whether the unit is quiet, stable and cheap to run. Modern units almost universally use EC dual-inlet centrifugal fans:
- Continuous duty at low speed. Ventilation runs around the clock, so the fan works far below its maximum. Because fan power falls with roughly the cube of speed, running slowly is disproportionately cheap — the core economics of these units.
- Low noise. A balanced double-inlet wheel and an EC motor without brushes keep the sound level low enough for bedrooms.
- Stable airflow. Speed control via the built-in electronics (with FOC vector control in the newest generation) holds the flow steady against filter loading and wind pressure.
- Demand control and connectivity. The speed interface plugs into the unit’s controls — and onward to building control — so ventilation can follow humidity, CO₂ or schedule instead of a fixed setting.
Our new-generation EC dual-inlet centrifugal fans, such as the SF146A-E092A3-02 with FOC vector control, were developed exactly for this role: quiet, stable airflow in a compact footprint.
Where HRV and ERV units go
The same unit architecture serves a wide range of buildings: houses and residential developments, hotels and villas, apartments, and office buildings. Wherever people stay for long hours and the building is reasonably airtight, mechanical ventilation with heat recovery pays for itself in comfort first and energy second.
Choosing between HRV and ERV
Decide in this order:
- Map your climate. Long, cold heating season points to HRV; long, humid cooling season points to ERV.
- Check your moisture problem. Dry winter air that cracks woodwork is a case for ERV; humid summers are a stronger case still.
- Size for continuous low-speed running. Pick the airflow for everyday occupancy, not for boost; the fan should spend its life in the efficient lower third of its curve.
- Inspect the fan specification, not only the exchanger. Noise level, speed control and EC motor efficiency decide daily satisfaction.
For how these units sit inside a wider ventilation strategy, see the commercial vs residential fan-system guide.
Bottom Line
HRV moves heat, ERV moves heat and moisture — and the climate you build in picks between them. Whichever the cabinet holds, the fan inside is now an EC dual-inlet centrifugal: quiet enough for bedrooms, stable against wind and filters, and cheap to run because it spends its life at low speed. Tell us your unit’s airflow and pressure target, and we will match the fan from our double-inlet centrifugal range.