A heat recovery ventilator (HRV) consists of two separate air-handling systems – one collects and exhausts stale indoor air; the other draws in outdoor air and distributes it throughout the home. In other words by mixing our “dry” fresh outdoor air with the moist indoor air the indoor air quality and relative humidity (RH) levels are controlled.
At the core of an HRV is the heat transfer module. Both the exhaust and outdoor air streams pass through the module and the heat from the exhaust air is used to pre-heat the outdoor air stream. Only the heat is transferred; the two air streams remain physically separate. Typically, an HRV is able to recover 70 to 80 percent of the heat from the exhaust air and transfer it to the incoming air. This dramatically reduces the energy needed to heat outdoor air to a comfortable temperature.
The HRV system installed in an R-2000 home can change all the air in the house over a three-hour period. Most HRVs are also equipped with automatic humidity sensors that increase the ventilation rate when needed – for instance, when you use the shower. Exhaust air is normally collected from the kitchen and bathroom areas, where most moisture and odours are created.
Although your HRV should have been balanced during installation, it is a good idea to have the system checked by a qualified contractor once a year. If you are purchasing an existing home that is equipped with an HRV, consider having the system serviced, including a balance test.
Why do we need an HRV?
Air infiltration has been reduced by the latest construction techniques to almost zero. Occupancy in this plastic envelope without controlled ventilation results in “sick building syndrome”. Allergies will result; mould spores will grow due to humidity levels in the envelope. Therefore, ventilation must now be done by mechanical means.
John Novak has been in the gas, heating and air conditioning business for over 20 years and is sought out as an expert in his field. For more information, tips and tricks feel free to visit his website at www.JohnNovakHeating.com
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