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Controlling Winter Humidity: When to use your HRV (ERV), Dehumidifier or Humidifier:

I recently visited a client who was running their Energy Recovery Ventilator (ERV) and a dehumidifier to dehumidify their home. At the same time they were also running a humidifier which had water literally running down the drain.

I turned off the dehumidifier and the humidifier (including the water) and increased the ventilation on the ERV to bring their humidity levels down. Why was this important? Because the excess humidity in the air had frozen on the inside of the cold concrete foundation wall during the extreme cold and with the quick thaw was now dripping out onto their basement floor.

Needless to say the client was not very happy, but the principal cause was excess humidity in their home and the customer not understanding how to operate their mechanical system. As we dropped the humidity in the home, the water on the floor dried up.

Here is a quick reference of when to use HRV/ERV’s, Dehumidifiers and Humidifiers

Dehumidifiers are much less effective and more costly to run in the winter than an HRV/ERV. Our recommendation is to use a dehumidifier in the spring and fall months when you are not running an air conditioner and there can be excess outdoor air humidity. You also may occasionally need a dehumidifier in the summer when the outside air gets extremely hot and humid and the air conditioner is struggling to keep up. (If your AC is running and the temperature is where it should be, but the air feels clammy, you might want to run a dehumidifier to assist the AC). Last summer we had about 3-4 weeks where this should have occurred. In a brand new home, you may need to run a dehumidifier somewhat longer while the home is drying out.

Humidifiers are common if you live in a drafty old home. In this case, there is a good chance that your home may be over-dry in the wintertime and you may even need to add humidity by using a humidifier. However, today’s highly efficient homes with ever tighter building envelopes do not lose the same amount of humidity than homes built only a few years ago. Customers used to a drafty old home expect to need a humidifier, but we try to discourage the use of them.

HRV / ERV’s are a very cost effective way of reducing indoor humidity levels when the outside air is colder than the inside air of the home, the colder the air the greater the capacity for an HRV/ERV to dehumidify. (An exception would be when there is a wet weather system in the area). Both HRV and ERV’s will help with winter humidity levels and provide continuous fresh air for better indoor air quality, however ERV’s have the added benefit of reducing over-drying the home in winter and reducing humidity gains in the summer, helping your air conditioner run more efficiently. One of the added benefits of the VanEE ERV that we supply to our customers is the Platinum control. If you are using an HRV, then a good rule of thumb would be to set the winter time humidity level to 30% and then monitor your moisture levels. If you have the VanEE ERV with the Platinum Control, it will do this work for you. There may be the occasional time where you might need to run the system on Maximum Ventilation if it is extremely cold outside. Remember the rule of thumb: If you see moisture building up on your windows, you have too much humidity and you need to run your ventilation system.