A heat recovery ventilator (HRV) is a ventilation system that uses a counter-flow heat exchanger between the inbound and exhaust airstreams of a building to provide fresh air and controlled ventilation.
A energy recovery ventilator (ERV) combines this ventilation system with the ability to transfer temperature and humidity in and out of a building.
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How It Works
An HRV is similar to a balanced ventilation system; however, an HRV uses the exhaust air from a building to either preheat or precool the incoming fresh air. An HRV typically features two fans - one to remove the air from within a building and one to bring in fresh air. What separates an HRV from other ventilation systems is the heat-exchange core. The core transfers heat from the exhaust stream to the incoming stream to warm the incoming air and reduce heating costs.
Where HRV's only transfer sensible heat (change in temperature), an ERV is able to transfer sensible heat and latent heat (heat given off or absorbed through a process) as well. The incoming fresh air is tempered with an energy recovery core. Heat is then exchanged through the core and water vapor is transferred with a rotating wheel, allowing for the transfer of humidity as well.
Like any part of an HVAC system, HRVs and ERVs need regular maintenance. Be sure to contact your HVAC consultant or service provider to schedule routine maintenance visits.
Below is a basic outline of an HRV/ERV maintenance schedule:
- Every 1 to 3 months: clean or replace filters, clean or unblock outside hooks and screens
- Every 6 months: inspect and clean heat exchange core, inspect condensate drain and pans
- Every 3 to 6 months: service and clean fans
- Annually: clean grilles and inspect ductwork, check defrost system, balance supply and exhaust airflow
- Lessens energy consumption and cuts operating costs by recalling heat and humidity from the exhaust air of the building
- Improves air quality by transporting fresh air into the building
- Betters work environment conditions by humidifying in the winter and dehumidifying in the summer
- Helps ensure ventilation and energy recovery standards are met
Every building needs ventilation to bring in fresh air, remove poor quality air, and control moisture. Due to these needs, most buildings are required to have a mechanical ventilation system to supply air from outside to the inside of the building.
Choosing between an HRV and ERV requires careful consideration of climate and other factors that affect indoor humidity levels. Building factors, such as the presence of a continuous vapor barrier, tight air sealing, and closed combustion can also increase humidity. In cold climates, high indoor humidity levels can be most effectively controlled in the winter using an HRV. However, for buildings that suffer from low humidity levels in the winter, an ERV is often a better choice. An ERV should also be chosen if it will be used frequently to ventilate an air-conditioned building in the summer.
To ensure an HRV/ERV system fits your building needs, contact an HVAC or engineering consultant. The consultant will assist in balancing the system and verifying flow to all the pickup points, as well as ensuring proper application (sizing, location of inlets and outlets, and zone control).
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