Basics of HRVs and ERVs and Their Benefits

by Rachel Laurendeau on May 30, 2012

In new home construction, houses are generally built airtight, meaning that there is minimal air escaping from the house or leaking in from outside through the walls, windows, doors, etc. Due to their tight construction, new homes need to have a mechanical ventilation system, preferably a balanced ventilation system using an HRV (heat-recovery ventilator) or an ERV (energy-recovery ventilator).

The Basics
The main purpose of these systems is to deliver fresh air into the home; they are not used as heating or air conditioning devices. In fact, these appliances work independently of your heating system.

The fan of the HRV pulls fresh air into the home while simultaneously exhausting stale air to the outside. Generally, the fresh air is vented into bedrooms and the living room while the stale air is drawn from bathrooms, kitchens and laundry rooms. As the two streams of air flow through the core of the HRV, the system “recovers” heat from the warmer stream and transfers it to the cooler stream. Basically, this means that in winter the unit recovers some of the heat from the already heated air rather than wasting it when it is exhausted.

An ERV can do the same things as an HRV but it also allows some of the moisture in the more humid air stream to be transferred to the air stream that is drier. Typically, the stale indoor air has higher humidity than the outdoor air in winter and vice versa in the summer.

Benefits of an HRV or ERV
• There is a constant supply of fresh air to the home.
• It provides fresh air and therefore improved air quality for the health of the home’s occupants, particularly those who suffer from asthma, allergies and other respiratory problems.
• Removes odors from the home.
• Dilutes indoor air pollutants.
• Lowers indoor relative humidity (although the jury is out on whether this is very effective in all cases and climates).
• Lowered humidity can translate to fewer problems with condensation, mold and fungal growth in the home.

Since HRVs and ERVs are still relatively new to the marketplace, many manufacturers and installers are not quite up to speed on all their ins and outs. If an HRV or ERV is being installed in your home, be sure to talk to your HVAC (heating, ventilation and air conditioning) contractor beforehand to understand which system is being used, how it will be balanced and who will be able to service it.

If you found this blog interesting, you might also like to read Clean Up Your Indoor Air.


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