Should you run your heat- or energy-recovery ventilator (HRV or ERV) in the summer?  The answer depends on your home’s air conditioning system, your ERV wall control, the outdoor temperature and, most importantly, the outdoor relative humidity.

As a rule of thumb, if you are more comfortable outside than inside your house, you should run your air exchanger in the summer.

First, let’s talk about ERVs.  An ERV works by exchanging your indoor air with fresh outdoor air, while recovering part of the heat and moisture difference in the airstreams.  Simply put, your ERV keeps the heat and humidity where they are. In summer, the heat and humidity are outside and your ERV will keep most of it from getting inside with your ventilation air.

If your indoor air and the outside air have about the same temperature and relative humidity (for example, if you keep the windows open), there is really no need to run the ERV in order to have good indoor air quality.

However, if you have air conditioning and the indoor air is cooler and dryer than the outside air, it is generally a good idea to run your ERV intermittently throughout the day.  Assuming you keep the windows closed while the AC is running, you’ll be needing fresh air to prevent CO2 buildup and to avoid that stale “airplane cabin” smell.  You can run your Aldes ERV intermittently depending on your wall control:

  1. Manual dehumidistat: Keep the dehumidistat set to OFF. If you have a timer wall control, you can use it to periodically run the ERV when the house is occupied, especially just before going to sleep.
  2. Mode control:  Set to OFF and use the timer as described above.
  3. Speed Control: Select the intermittent setting (20 minutes low speed exchange followed by 40 minutes off).
  4. Digital multifunction control: Select ECO 2 mode (20 minutes low speed exchange followed by 40 minutes off)
  5. Electronic Humidistat with LCD: Select the intermittent mode (20 minutes low speed exchange followed by 40 minutes off).

Running your ERV to get fresh air instead of opening the windows will have the added benefit that the incoming warm air will be partially pre-cooled and dehumidified thanks to the energy-recovery core.  The air conditioner will not have to work as hard to bring the fresh air to your desired temperature.

What about HRVs? If you have an HRV (heat-recovery ventilator) rather than an ERV, the only difference is that the humidity in the outdoor air will pass through the HRV core without any moisture transfer, and the cooler indoor air may feel damp (because cold air has less ability to contain water vapour than warm air).  You may consider using a dehumidifier in addition to the air conditioner.

How can you tell if you have an Aldes HRV or ERV?  Just have a look at the model number: if it starts with an “E”, you have an ERV; if it starts with an “H”, it’s an HRV.

In order to maximize your house’s indoor air quality and consequently your health, you should take every opportunity when the outdoor conditions are comfortable (for example at night) to run your air exchanger.



One Comment

IAC-Indoor Air Care

Thanks for the post. Looking forward to the
next. We’ll share this to our own followers! Don’t
forget to clean your air ducts and hvac from dirt, dust, and mold.


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