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How To Properly Vent A Bathroom Fan

June 28th, 2024 | 4 min read

By Kilian Agha

Whether setting up your first bathroom exhaust system or fixing your kitchen range hood, you want to be sure you're doing things right. Where should the moisture from your bathroom and kitchen vent to?

South Central Services began in HVAC and refrigeration. We transitioned to insulation due to the close relationship between insulation and HVAC. Insulation is the first defense of your home's environment, but HVAC plays a vital role in maintaining the environment that insulation enables. Where moisture and heat are directed matters for you and your home's health.

By the end of this article, you’ll understand:

  • Where vents often direct hot and humid air
  • Where vents should be directing humidity
  • How common vents can be set up properly
  • Who can redirect improper vent systems

Vents Should Be Directed Outside Of Your Home.

When set up correctly, vents dump hot and humid air outside your house. The idea behind having vents in areas like the bathroom and kitchen is to ensure your home doesn't face excess humidity.

Unfortunately, many bathroom fans, kitchen range hoods, and dryer vents dump humid air into other parts of your home. Moving the humidity from one room to another can prevent humidity build-up in the bathroom or kitchen. However, the moisture and the problems it can cause are simply relocated to another area of the home.

Excess humidity can lead to mold, mildew, and wood rot concerns. If your home has more water content in the air than the air can cold, the vapor will condense. Not to mention, an incredibly humid home is not a comfortable living environment.

If vents do not direct hot and humid air outside of your home, then the purpose of the vent is wasted.

How Should Bathroom Fans Be Set Up To Vent Outside?

Many bathroom fans are set up to vent into the attic space. We see this often when we retrofit an attic with spray foam insulation on the floor or the underside of the roof. The moisture is directed into the roof rather than the humid bathroom air exiting through the roof or soffits.

In bad cases, the roof can experience wood rot. Whenever we insulate an attic and notice these vent problems, we work with the homeowner to redirect the humid bathroom air outside. This redirection can work with a roof, soffit, or wall.

It is also essential to place the vent in the right location in a bathroom. Some bathrooms are quite large or are broken up. The vent should be closest to the most significant source of humidity: your shower.

How Should Kitchen Range Hoods Be Set Up To Vent Outside?

Some kitchen range hoods direct the humidity of the stove and oven outside of the home. However, there are range hoods that allow the moisture in the air to circulate inside.

An example is the "microwave range hood" in many kitchens. Often, these microwave hoods are not connected to a vent. Instead, they redistribute the humidity of the kitchen throughout the home.

Unlike the bathroom fan venting into the attic, which aggressively impacts a specific area of the home, these range hoods impact everywhere throughout the house. This high humidity level affects your comfort and the energy efficiency of your HVAC system. When the humidity level inside rises, the HVAC system must overcompensate to address the moisture. Or, the HVAC equipment may not be sophisticated enough to address the humidity, which leads to mildew and mold.

Kitchen range hoods should be connected to a vent. Like bathroom fans, they can be vented through the roof, a soffit, or a wall.

How Should Dryer Vents Be Set Up To Vent Outside?

You may not initially think of your dryer as a source of humidity. However, your dryer vent is responsible for disposing of hot and humid air. The moisture of your clothes, wet from the washing machine, has to go somewhere.

Dryer vents are sometimes set up to ventilate into a home's basement or crawl space. This system is incredibly problematic due to the nature of condensation. When a dryer vents hot and humid air into the cold of your basement or crawl space, the cold air below the ground cannot accommodate all the moisture.

Hot air holds more water vapor than cold air. When the air becomes saturated or reaches dew point, the vapor condenses into liquid water. These areas face enough humidity and vapor transfer already.

Dryer vents should be directed outside. Most commonly, dryer vents can vent through a wall. However, the roof or a soffit can also be used for dryer vents.

Properly Vented Exhaust Supports The Health Of Your Home.

While it may be difficult to believe, proper ventilation can make a noticeable difference in your home's energy efficiency, comfort, and air quality.

Take your kitchen range hood as an example. When you cook, the humidity can be mixed with VOCs and cooking odor. By terminating your ventilation outside of the home, the moisture, smells, and low-quality air are removed from your home. With the microwave range hood, that mix of air would just be pushed throughout your home.

Excessive humidity, given enough time, can develop into mold and mildew. Anyone with a mold issue knows firsthand about the importance of existing in mold-free spaces. Even without a specific allergy, mold is not good to live around and will cause health concerns.

Rather than investing in HVAC to address excess humidity, it is a wiser financial decision to prevent that excess humidity in the first place through appropriate vents.

If your home is not smelly or sticky from humidity, it will be much more comfortable to live in. The comfort of your home is also related to your insulation, but it is important to address insulation and HVAC in tandem.

As for your energy costs, whatever HVAC equipment you have runs overtime when the home environment is disrupted. Whether it is a change in temperature or humidity, the HVAC will run up your energy bill, trying to correct the problem. By appropriately venting your bathroom fans, kitchen range hoods, and dryer vents, you can save your HVAC from trying to solve an unnecessary problem.

Can I Fix The Vents In My Home Myself?

Handy homeowners may be able to fix these problems on their own. Most homeowners should be able to identify vent problems and where their humid air is being dumped inside the home. This information is vital for whichever professional you contact to fix your vents.

We recommend contacting HVAC contractors, electricians, or handymen for vent concerns.

The Bottom Line About Proper Ventilation For Humidity In Your Home

The purpose of a vent is to prevent humid air from interfering with your home environment. The only way to ensure the humidity will not exist elsewhere in your home is to ensure the vent terminates outside the house. The humid air must be dumped outside whether the vent runs through your roof, a soffit, or a wall.

Bathroom fans, kitchen range hoods, and dryer vents are all examples of vents needing to direct hot and humid air outside the home. Too often, these vents circulate humidity or dump the humidity in another place, like the attic or crawl space. Correcting this problem will save your home from mildew and mold concerns.

Now that you know how vents should be set up to deal with humidity, your next step is to:

Kilian Agha

Kilian has co-owned and operated South Central Services for 8 years. He is passionate about community involvement. In his spare time, he enjoys being with his family, playing ice hockey, and going fishing with friends.