Can I Turn Off The Fan That Brings In Outside Air?

Everybody loves fresh air. At least everybody I’ve ever known any way. But before you turn off or block off that fresh air intake vent, take just a moment reading this article and understand a little bit about why you have a fresh air vent in the first place.

Lack of fresh air in your home can cause toxins to exist more readily in your home. When fresh air is forced into a home it replaces the stale air that exists by forcing the stale air outside.

Just so you know right off, yes you can turn off that fan that brings in outside air but you could be allowing these harmful gases to be more present in your home.

It’s the fresh air duct, fan, or vent that brings in fresh outside air and displaces those gasses that come from wood products, furniture, or even smoking. If you smoke or have smokers in your home don’t block or turn off that vent.

The reason I mention “air duct, fan, or vent” is because fresh air is introduced into homes in more than one way. There have been several designs and methods developed to make air changes in a home. Even those that incorporate even a forced air furnace to bring in nice outside air.

Even some windows have slots at the top with a slide that allows you to open or close the vent thus allowing you to keep out the extreme weather.

Another thing to research would be the type of construction materials that exist in your home. Each building product has a different length of time that they off-gas.

If you understand the materials in your home and determine the length of time they off-gas you can make a safer bet as to when you should plug up or turn off that outside air vent.

But most materials only off-gas for a short time. When they are done off-gassing then you are left with a fan that is bringing outside air into your home in the heat of summer and the cold of winter.

Really though, if you know a little about the materials your house was constructed of and how old those materials are then you can make an honest to goodness judgement about if you need that fan or not.

Fan is on, illustrated by a piece of tissue being sucked up onto the grille

You know those tags on your pillows that said “do not remove this tag under penalty of law”? Like the tag police, are the fresh air police gonna come check your outside air fan and fine or arrest you?

Too many laws and regulations. It’s about government trying to keep us safe. Can we think for ourselves? Make judgments for our own welfare? And they are probably doing the right thing because some people obviously don’t make good judgements.

What Do The Materials In My House Construction Have To Do With My Outside Air Fan?

If you have never bought a new car then you’ve at least experienced that new smell that just grabs you by the heart strings as you slide down into that new upholstery and close the door.

Who ever thought that such an inviting smell could be hazardous to your health?

Just like a new car, another good example is a mobile home, when new, they have this special odor that is a result of the off-gassing of materials in the home. These gasses are mainly formaldehyde.

The off-gassing comes from a variety of things including, but not limited to, carpet, furniture, and a bunch of different kinds of building materials.

The outside air fan or system that is supposed to replenish the gassy air in your home is essential when your home is new.

According it there are four basic types of home ventilation systems.

  1. Exhaust
  2. Supply
  3. Balanced
  4. Energy Recovery & Heat Recovery Ventilators

New products have hit the market in resent years and they have developed ways to allow you to run an air changing system that can keep those air changes going year around in even the coldest or hottest weather.

They work on the principle of a heat exchanger. There is a huge variety of air exchangers available.

Price varies extremely so don’t let this high priced unit scare you off. look around and you’ll fine something to your liking. You can scope out a few here on Amazon (#ad) to get an idea of the size and construction.

Believe it or not these heat exchangers are relatively easy to install. Some duct work, but for those of you inclined to DIY it’s not too tough to do.

What Kind Of Whole House Ventilation System In Mobile Homes?

Mobile homes incorporate what would be called a supply type of fresh air system. If you have a mobile home you can see a duct at the top of your furnace.

The duct size varies but would be a 4 to 6 inch piece of insulated flex duct hanging from the ceiling in the same cavity as the furnace. The duct is attached to a vent at the top that bring in fresh air from the roof when the fan is running.

The bottom of the duct is usually tied to a damper that opens when the fan comes on and closes when the fan is off to help prevent air movement when the system is off.

There is no prevention in this system to stop the really cold air from winter and the really hot air from summer from entering the home when the fan runs.

This is the system that uses the small slots at the top of windows or some other sort of relief to exhaust the air. Sometimes its a ceiling fan on a timer or switched on when the fan is running with that outside air damper open.


Spend some time checking out what kind of fresh air system you may have. I live in a house built in 1937. I’ve done some extensive remodeling. Two new heat pump systems. Complete new electrical wiring and plumbing.

Some additional square footage with new windows in the new additions. But the rest of the house has the original windows with leaded panes at the top of the double hung windows.

That’s my fresh air. As houses age, the gaps widen. My wife just wouldn’t let me change out that old look. They are pretty cool windows. Pun intended

Chad Peterson

Chad Peterson is a veteran of the HVAC industry since 1977. "I like to explain heating and air conditioning problems in a way the average home owner can understand. "

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