I have recently moved in a house built in 2021. Its been a couple of months but I noticed today that there is an exhaust vent that is continuously running in the laundry room and there is no switch for it that I can find. Also there is an air went that is continuously running right outside the laundry room blowing cold air. My HVAC system is turned off, seems like a fan running and blowing cold air from outside. Is it something that is common? Any suggestions would be great.

Update: both the ducts lead to the attic, The one in the Laundry room is right next to the AC/HVAC duct. I do not have access to the attic right now.

  • Surely you can find the device that's moving air through the vent by sound, no? My hunch is an energy recovery ventilator, but your situation sounds odd.
    – isherwood
    Commented Oct 30, 2023 at 19:47
  • This exhaust fan is removing air from the laundry room? Where does this air go or come from? Is "outside the laundry room" still within the house or venting exterior to the house? Is there a crawlspace under the 2021 house?
    – popham
    Commented Oct 30, 2023 at 20:22
  • The attic connection likely rules out a radon mitigation system.
    – HABO
    Commented Oct 31, 2023 at 3:19
  • 1
    Thanks @FreeMan I have got my account fixed.
    – Sam
    Commented Oct 31, 2023 at 19:33

1 Answer 1


2021 build, fan that runs constantly, you have exhaust and incoming air. It's either an Energy Recovery Ventilator (ERV) or a Heat Recovery Ventilator (HRV.)

Assuming a competent design, which type you have depends on the climate where the house is.

Rather than "ventilation by random leakage" you have a tightly sealed building envelope, and a pair of fans that remove stale air and supply fresh air, passing the airstreams through a heat exchanger core so that some percentage of the heating or cooling energy applied to inside air is recovered and applied to the incoming air (which random leaks don't do.)

A HRV just does heat exchange. An ERV exchanges both heat and humidity.

  • Thanks for your response, I have some more questions. Does the ERV and HRV both run Fans 24/7 ? as in my case I see that its running continuously is there any way to control it ( I noticed that when i tripped the breaker marked as Furnace the Fans and the HVAC system stopped working). Will it cause any harm since the airquality outside my home is not very good. Secondly its cold now and I have noticed that the blower is pushing colder air in which feels like AC. Anything of concern here? I turned OFF my AC breaker last night, not sure if it was a problem or it is by design.
    – Sam
    Commented Oct 31, 2023 at 19:32
  • It is normal to run 24/7. Some are set up to run other ways (X minutes per hour, low speed always & higher speed when motion is detected or humidity in the bathroom, etc.) Since the heat exchange isn't 100%, the incoming air will be cooler in winter and warmer in summer than inside air. If the builder cheaped out, the exchange efficiency will suffer (more efficient ones cost more.) The reason for having it at all is that the air quality inside an unventilated well-sealed house becomes quite bad.
    – Ecnerwal
    Commented Oct 31, 2023 at 20:38

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