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10 Reasons Why a Bath Fan Should Not Be Vented Into Another Room

Your bathroom exhaust fan is meant to keep moisture levels down by sending out damp, humid air and pulling in cool, dry air. Where your fan sends air matters for this process. Your bathroom fan should never exhaust into another area of your home, and here’s why.

1. You Will Be Violating Building Codes

Building codes exist to keep homeowners safe. It is important to obey building codes (unless grandfather clauses or other exemptions exist) to stay on the right side of the law and to stay safe.

The IRC states that the bathroom exhaust needs to be exhausted out of the house.

Section M1501.1 states:

“The air removed by every mechanical exhaust system shall be discharged to the outdoors in accordance with Section M1504.3. Air shall not be exhausted into an attic, soffit, ridge vent, or crawl space.”

Bathroom Fan Vented Down & Outside the house

You can read the Reasons Why a Bathroom Fan Should Not Be Vented Into a Crawl Space and Reasons Why Bathroom Fan Should Not Be Vented Into an Attic to see why these two areas were specifically named in the IRC prohibition.

The IRC also mandates where this vent needs to be located by defining how far it must be from property lines (3 ft), gravity air intakes, windows, or doors (3 ft), and mechanical air intake openings (10 ft unless the intake opening is below the vent, then 3 ft).

Violating building codes is not only unsafe but also costly. Homes that are not up to code cost more in insurance (if they are covered at all) and sell for less.

2. Furniture and Fabrics Can Be Damaged

There is a reason why museums are kept cool and dry.

You don’t want wet air from your bathroom pumping into your living room, ruining your grandma’s antique curtains and your new expensive couch.

Damp fabrics can become mildewy and stained. Sometimes the stains may look yellow or brown, but they can be white as well. Water damage can also cause some fabrics and carpeting to fall apart.

If your furniture, clothes, or other fabric items become water damaged, it can take a lot of work to restore them, or they may be irreparable depending on the extent of the damage.

In addition to smelling and looking bad, water damage can lead to mold formation, which can be harmful. Mold needs to be removed as soon as it is recognized. The only way to prevent re-growth is to remove the source of the water.

3. Walls, Floors, and Ceilings Can Become Damp

Excess moisture is a serious business when it comes to the structural integrity of your house.

Floors, walls, and ceilings near bathroom exhaust vents that become soggy can risk deteriorating and caving in in addition to looking and smelling bad. Indicators of excess water include leaking, window condensation, visible mold growth, moldy odors, and stains.

Dampness can also attract termites and some wood-rotting fungi species, which further threatens the structure of your house.

If you notice tell-tale signs of water damage to your walls and floors, especially loadbearing walls, it is essential to first get your home inspected to see if is safe to be in.

Next, it will be essential to make repairs and re-route your bathroom exhaust system to the outside, following Section M105.3 of the IRC’s standards, to prevent further damage to these areas.

4. Mold Can Grow in the Room

No one wants to see mold growing on their walls or smell its pungent odors in their home. But if your bathroom exhaust is pumping into another room in your home, mold may become an unpleasant reality even though you have prevented the mold from growing in your bathroom itself.

In addition to being gross, mold growth can be dangerous.

Molds such as black mold can be a serious health risk to those with compromised immune systems and several molds produce allergens as well. People with asthma may have their symptoms worsen being around this type of mold.

Certain types of molds can also jeopardize the safety of a home by producing wood-rot and breaking down wooden structures.

If you notice slight mold growth in your home, it may be able to be removed using bleach and water. Make sure to wash and disinfect the area after the fact to prevent re-growth. For more severe mold issues, contact a professional for guidance.

A Man removing Mold fungus with respirator mask

5. Dangerous for Electrical Systems

Water is a highly conductive material, which is why hair dryers or other plugged-in appliances should stay out of the bathtub. This is also why outlets in the bathroom need to be protected from moisture.  

Plug points, etc., in bathrooms are carefully regulated because of the moist environment of bathrooms. Bathroom outlets in newer homes are protected by GFCI outlets, which turn off the electrical current when it becomes a shock hazard.

Other rooms are not generally required to have GFCI outlets since the level of moisture does not usually require them. However, if excess moisture is being ventilated from the bathroom into a room with unprotected outlets, this room becomes hazardous.

Rooms with unprotected outlets have a higher risk of shock, fire, and/or failure in the presence of moisture. These risks are accelerated when the rooms with the moisture also contain subpanels or exposed wiring.

6. Bathroom Smells Will Be Released Into the Room

Let’s face it. Bathrooms come with unpleasant odors. The last thing anyone wants is to have those bad smells leave the bathroom and enter a different room of the house.

When an exhaust fan pumps out moisture from the bathroom, along with the moisture any unpleasant smells are exhausted as well.

If your exhaust fan pumps into a different room, say the bedroom, living room, or kitchen, it is spreading all that bathroom odor throughout your home. Not only does this make your living space less pleasant for you, but it could also cause embarrassing situations and lower the house’s market value.

Avoid awkward and unpleasant situations by making sure that your bathroom fan exhaust system is up to code and pumping smells out of the house rather than into a different room. You will save yourself the embarrassment and increase the value of your home in the process.

7. Hot, Moist Air Can Be Unhealthy

There is a link between breathing in hot, moist air and airway inflammation. This can be a problem for asthmatics and people with COPD who already have airway inflammation that causes breathing problems.

Hot and damp air also becomes a breeding ground for mold which can cause symptoms of wheezing, stuffy nose, or red or itchy eyes or skin for people who are sensitive to it.

Even otherwise healthy individuals can suffer from increased coughing, wheezing, or other upper respiratory symptoms due to mold exposure.

Mold has a much worse effect on individuals with immune suppression or lung disease. These people are more susceptible to fungal infection due to mold exposure.

4 Ply Disposable Face Mask Protective(50PCS), Elastic Earloops, Single Use- Green

People with chronic respiratory diseases such as asthma or COPD may experience increased difficulty breathing due to mold exposure.

Dust mites are also attracted to moist environments, and they can cause an increase in allergies and asthma in individuals who already suffer from these health concerns.

8. A/C Bill Will Go Up

The humidity of your bathroom will heat up the inside of your house if your fan is designed to pump into the house instead of out of it. This is going to increase the heat of your living space.

While this may seem like a perk in the winter, you are not going to enjoy the increased electricity bill come summertime. To counter the hot and moist air being dumped into the room, you will need to blast your A/C to keep up.

The addition to your energy bill could be as much as a hundred dollars or more per month, which anyone would agree can be better spent elsewhere.

Re-routing your bathroom fan to the outdoors will pump the bathroom humidity outside and save you some extra cash come summertime.

9. Exhausted Air Can Get Pulled Back Into Bathroom

Pumping your bathroom’s exhausted air into another area of your home can defeat the purpose of your bathroom ventilation altogether.

Exhaust fans create negative pressure in the bathroom. Hot, humid air from the bathroom is pushed out and then air from outside and other rooms is pulled in to replace it.

If your fan vents into an adjacent room, then the same moist, hot air will have nowhere to escape, and there won’t be any cool, dry air to replace it. The same damp air will be pulled back into the bathroom.

Not only will this completely defeat the purpose of bathroom ventilation, which is to help maintain air quality and indoor climate, it can also cause a variety of problems that come from poor bathroom ventilation.

10. Insects and Vermin Love Moist, Warm Environments

If the idea of dust mites, mold, and termites isn’t enough to convince you to send your bathroom exhaust outside, maybe mosquitoes, mice, and flies will.

Many of our least favorite vermin and insects prefer to live in hot, moist environments for nourishment and warmth.

Mosquitoes and flies prefer moist environments, and mice have also been known to gravitate towards water. These pests are fast breeders and can be carriers of diseases and bacteria.

Other bugs that are drawn to moisture and mildew include springtails, psocids, cocroaches and foreign grain beetles. These tiny bugs have been known to infest homes where areas of high moisture are present.

While these particular bugs are not harmful, they are considered nuisance insects and are highly unpleasant.


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