How To Vent A Bathroom With No Outside Access

[BLOG] Published: 2021-12-07 - Updated: 2023-02-09

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How To Vent A Bathroom With No Outside Access

The wettest room in your house is your bathroom. Showers that are steamy, toilets that flush, sink that run and the occasional drips add up to a lot of moisture. These conditions can lead to mold, mildew, and other unpleasant issues.

Does a Basement Bathroom Need a Vent? Yes, every bathroom needs to be ventilated. 

It is required by code in many places for building contractors to ensure adequate ventilation in bathrooms. 

They do not always do so. This usually results in insufficient ventilation, which can lead to future issues. Installing a ceiling vent is the simplest way to vent such a bathroom. There are, however, other possibilities to consider.

Bathroom Ventilation And Building Code

Let's first look at the building code requirements before we can solve the bathroom's ventilation problems.

Bathrooms must have proper ventilation to eliminate odors and excess moisture. There is more moisture build-up in the bathrooms as technology improves. When you take a hot shower, condensation forms on the walls and windows, fogging all of the mirrors.

Most municipalities' current building codes require bathrooms to be vented. This can be done through an operable window or an exhaust fan. However, keep in mind that the window option is merely a minimum requirement.

 As a result, it cannot be considered a reliable or effective ventilation system. (Upgrade Home, 2021)

How To Vent A Bathroom With No Outside Access

Common Indicators That Your Bathroom Needs To Be Ventilated More

Excess Moisture

Showers, sinks, and tubs are found in almost every bathroom. This means that even if you don't use your bathroom very often, it will have lingering moisture if it isn't well ventilated.


Have you ever been in a room with poor air circulation? You probably noticed how suffocating the atmosphere was. Now imagine the situation in a bathroom and just how a little stuffy and uneasy it would be for you.


This is the most common issue in bathrooms with poor ventilation. Because moisture is trapped in these bathrooms for longer periods of time, mold and mildew thrive on the walls and tiling.

Mold in the bathroom is extremely dangerous. It can cause a variety of allergic reactions and respiratory illnesses.

Stained Ceiling 

You don't have enough ventilation if there are stains on your walls or ceiling. It means that the moist bathroom air has caused an excess of moisture in the house.

Smells That Stay

If you're going to use a combined toilet and shower, make sure there's plenty of ventilation. Imagine a situation where someone has used the restroom and you want to shower in a few minutes. You’d probably not be able to handle the stench, right?

The smells from the toilet tend to linger for a long time in a poorly ventilated bathroom or toilet. Even after 30 minutes or more, don't be surprised if the bathroom smells. (Expert Home Report, 2021)

ProTip Takeaway: With poor ventilation, it will take a long time for the bathroom to dry after you've used it. For example, it will take some time for the shower area to dry after you have taken a shower.

How do you vent a bathroom when you don't have access to the outside?

There are various options available to you if you need to vent your bathroom but don't have access to the outside. These unusual installations will need a bath fan and the services of a professional HVAC contractor. You can create proper ventilation using the following methods.

Use of a ceiling vent

Installing a ceiling vent is probably the most efficient way to ventilate a bathroom with no outside access. A ceiling vent is a unique machine that allows air to escape from the bathroom. In other words, it's a machine that, like an open window, allows moisture to escape from your bathroom.

Installing a ceiling vent in your bathroom will ensure that it does not remain humid or moist. If you are unable to install it yourself, you should hire a professional to do so. (Vircet, 2020)

ProTip Takeaway: A light fixture is found on the majority of ceiling vents. As a result, they can function as both a ceiling vent and a light source.

vent bathroom

Using a floor duct vent

Venting through the roof is impossible if your bathroom is located away from your exterior wall. This is a common problem in bathrooms located beneath a stairwell.

In bathrooms without outside access, duct vents can be used to ventilate bathrooms if ceiling venting is not possible.

 A floor duct vent is a special machine that uses floor grates to remove moisture and bad air from your bathroom.

In other words, a floor duct vent provides an additional exit point for noxious odors and reduces moisture levels from your bathroom. This is accomplished by creating, opening, and drawing air out.

Ceiling vents are considered to be more efficient than floor duct vents. This is despite the fact that floor duct vents are effective.

ProTip Takeaway: Inquire with your HVAC contractor about extending a bath fan through the floor. In this case, the plumbing vent runs between the floor joints and out the exterior wall.

Using extra ducts

The lack of ventilation in your bathroom could be due to the fact that there is only one-floor duct when two or three are required. So, if the one-floor duct isn't providing enough ventilation, you should add another.

If one of your bathroom's ceiling ducts isn't working properly, the situation is similar. To increase ventilation power, simply add one or two more ceiling ducts. (Vircet, 2020)

Vent Through The Joist

Venting through the ceiling is similar to this method. Instead of relying on a complex ductwork system, you'd cut a hole in the first-floor joist cavity to vent your bathroom air to the outside. This is an inexpensive and effective way to ventilate the air in your basement bathroom.

The difficulty of installing venting through this joist cavity is the issue. Floor joist cavities are cramped, difficult-to-work-in spaces. You may also encounter pipes or other obstructions that you must workaround to get your ductwork through.

Vent Through The Joist

Using The Right Bath Fan

The HVAC contractor will install the proper bath fan. He will also set up a proper ventilation system from the bathroom to the nearest exit point. It allows the fan to move moisture and odors from the bathroom to the outside. As a result, the bathing area remains dry and sanitary.

The size of a bath fan refers to how much air it can move at any given time. The fans' size is measured in CFM (Cubic Feet per Minute) (CFM). It refers to how much air the fan can remove in one minute in cubic feet.

A fan with a capacity of 1 Cubic Foot per Minute (CFM) is required for every square foot of bathroom space. For proper efficiency, a standard bathroom would require a venting fan with a 40CFM capacity.

You'll need to accurately determine the frequency of bathroom use in addition to the bathroom size. If multiple people share a bathroom, for example, you'll need a fan with a slightly higher CFM rating. (Planted Shack, 2021)

Using A Recirculating Fan For A Half Bath

It's important to remember that a recirculating fan does not exhaust air to the outside. It purifies the air in your bathroom through a filter, ensuring that all odors are eliminated. Because there are no installed showers, the moisture level is deficient. It is, therefore, an excellent choice for half baths.

ProTip Takeaway: If your morning schedule is hectic, consider installing a bathroom vent fan with an automatic humidity sensor. These units detect when humidity levels are too high in the room and adjust the fan speed.

Hire A Professional

Ventilating your bathroom on your own can be too difficult and something might go wrong. You should therefore hire a professional.

 Professionals are trained to deal with a variety of situations. They are also able to ventilate almost any space. Most homeowners do not have the knowledge or tools to install certain types of ventilation systems.

The only disadvantage to hiring a professional to install new ventilation is that it is usually costly. As a result, you should only hire a professional to install or improve bathroom ventilation if you're certain you can't do it yourself. (Expert Home Report, 2021)

ProTip Takeaway: Hire an HVAC contractor when installing the vent beneath the bathroom to the exterior space.

Wipe up any puddles

Drips drop, and puddles should never be overlooked. Immediately wipe up any pools of water you notice with an absorbent bathmat.

 A puddle-free bathroom floor is very safer. It also ensures that the full bath dries out as quickly as possible during the 15+ minutes of fan run time. This helps in preventing mold and mildew spore growth.


Installing a Bathroom vent with no outside access will require the services of an experienced contractor if you are in Houston Texas. The contractor will assist you in determining which method is most appropriate for your situation.

Smart Remodeling LLC is the best bathroom contractor in Houston. We are licensed bathroom design and remodeling pros with the most comprehensive selection of services in the area. Schedule your free bathroom remodeling consultation today through our website. You can also call us at 832-800-8889

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