A Heat Recovery Ventilator (HRV) is an energy-efficient ventilation system that improves indoor air quality while minimizing heat loss or gain in a building. HRVs are commonly used in residential and commercial buildings to provide fresh air and exhaust stale indoor air. Here's how an HRV works:
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Air Exchange: The HRV system consists of two separate air streams: the supply air stream and the exhaust air stream. These air streams run through the HRV unit, but they do not mix.
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Indoor Air Intake: The HRV draws in indoor air from various rooms in the building through a network of ducts. This indoor air contains pollutants, moisture, and often heat (especially during the heating season in cold climates).
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Outdoor Air Intake: Simultaneously, the HRV draws in fresh outdoor air from outside the building through another set of ducts. This outdoor air is typically colder and drier than the indoor air.
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Heat Exchange Core: Inside the HRV unit, the two air streams pass through a heat exchange core. This core is designed to transfer heat and moisture from the indoor air (exhaust air) to the outdoor air (supply air) without allowing the two air streams to mix. The core may consist of heat-conductive materials or a rotating wheel.
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Heat Transfer: During the winter heating season, the warm indoor air passing through the heat exchange core transfers its heat to the cold outdoor air without the two air streams physically mixing. This process is called heat recovery. As a result, the supply air becomes pre-warmed before entering the living spaces, reducing the energy needed to heat it further.
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Moisture Transfer: In addition to heat recovery, HRVs can also transfer moisture between the air streams. This helps maintain proper indoor humidity levels by preventing excessive drying of the indoor air during the winter and reducing excess humidity in the summer.
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Distribution: The pre-conditioned supply air is then distributed to various rooms in the building through a separate set of ducts, providing fresh air to occupants.
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Exhaust: Simultaneously, the stale indoor air is exhausted from the building through dedicated exhaust ducts. The exhaust air may pass through the heat exchange core to recover additional heat before being expelled.
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Control: HRV systems are equipped with controls and sensors to manage the air exchange rate, adjust fan speeds, and optimize the balance between indoor air quality and energy efficiency. Some HRVs also have frost prevention features to prevent freezing of the heat exchange core in cold climates.
The primary benefits of HRVs are improved indoor air quality by constantly providing fresh outdoor air and energy savings through heat recovery. They are especially effective in cold climates where providing fresh air ventilation can otherwise lead to significant heat loss during the heating season. Proper maintenance of HRV systems, including regular cleaning and filter replacement, is essential to ensure optimal performance and indoor air quality.