How To Vent A Bathroom With No Outside Access: 5 Solutions

Most building codes require homeowners to install a vent fan in bathrooms with no windows and no outside access for an exhaust fan. The task seems downright daunting, but there are several options you could consider.

The easiest way to vent a bathroom with no outside access is by installing a ceiling vent. Alternatively, you could expand the bathroom ducts or vent beneath the floor. In a half-bathroom or guest bathroom, you can install a recirculating fan to keep odors at bay.

Do Bathroom Exhaust Fans Need to be Vented Outside?

We all know that a well-ventilated home is drier, healthier, and more comfortable. The only way to ensure an adequate comfort level and prevent mold and mildew development is by getting moisture outside of your dwelling. To do that, the bathroom fan – and all other extractor fans you might have in your home – must be vented outside.

What are the code requirements for venting a bathroom fan?

Bathroom fans are not required by all building codes, but the requirements change from municipality to municipality. However, all bathrooms are required to have ventilation (be it a window or a fan).

Thus, if your bathroom doesn’t have a window and no access to the outside, a fan is a must-have. That said, you must check with your city’s planning and permitting department to find out whether a bathroom fan is required and, if yes, what types of fans you can install.

The codes also highlight where a bathroom fan can be vented; long story short, it should always vent to the outside.

You can’t vent a fan in the attic, soffit, or another enclosed space. With this in mind, projecting the venting system for a bathroom with no outside access can be challenging. Worry not, though. Keep reading to find the right solution for you.

7 Signs That Indicate Your Bathroom Has No Proper Ventilation System

Proper bathroom ventilation is essential for more reasons than one. High moisture levels create the perfect environment for mold and bacteria to thrive. Moreover, moisture trapped in the room also leads to other problems, like condensation, which could damage your walls and furnishings. Here are a few signs your bathroom venting system is not working properly.

1. Mold and Mildew

Black stains on your ceilings and walls are the first signs of an improper ventilation system. Bathrooms are highly wet areas that need good airflow to wick moisture and cool off the warm air.

If your bathroom doesn’t have a window or proper vent, all that warmth and humidity remain trapped inside. Mold and mildew thrive in a warm and moist environment, so you’ll start noticing black spots on your walls and ceilings, but also inside your bathroom cabinets.

The problem may not be immediately visible on tiled walls, but the fungi will eventually make their way out through the grout, staining it.

From the bathroom, mold and mildew can infiltrate other areas of your home, especially inside the walls, where they can damage the wall studs. Moreover, mold is also responsible for respiratory infections.

2. Condensation

In addition to mold and mildew, trapped moisture can set on the ceilings and walls. When the warm air touches the colder surface, it precipitates and creates water droplets. If left unattended for too long, the high levels of humidity can start to damage your bathroom furniture, walls, and ceiling.

Like mold and mildew, condensation is also responsible for a number of health problems, including respiratory infections.

3. Musty Smells

Poor air quality inside your home is almost always synonymous with foul smells. Moisture in the bathroom generally gives off a musty smell that can impregnate the walls and your towels and clothes if you’re washing or drying them in the bathroom.

The offending odor isn’t harmful on its own, but it’s always an indicator of a bigger problem, such as mold and bacterial growth.

4. Persistent Sore Throat

Not many people link a sore throat to a poorly vented bathroom, but the lack of ventilation could be the cause of your illness.

We mentioned mold and mildew above (both of which can cause respiratory infections), but they are not the only nasty germs that can grow in a wet bathroom.

Bacteria also thrive in this environment. Two of the most common types are staphylococcus and streptococcus. Both types can live on our skin or inside our bodies without creating any harm. However, they can become less benign and more opportunistic through constant exposure.

Considering that we spend about half an hour a day in the bathroom, on average, we breathe in quite a lot of these bacteria if they happen to grow in your space.

More often than not, they end up in the throat and are responsible for common colds and throat infections. However, they can occasionally make their way to the lungs, causing severe respiratory infections, bronchitis, and other ailments, some of which can be life-threatening.

Another type of bacteria commonly growing in poorly ventilated bathrooms is Serratia Marcescens. This is another opportunistic pathogen that you can observe developing as an orange slime growing inside your toilet, shower, or even on the tiled floor.

The pathogen has long been considered harmless, but studies now confirm that it can cause a wide range of diseases, including pulmonary infections, urinary tract infections, peritonitis, and, sometimes, life-threatening bacteremia.

5. Peeling Walls and Ceiling

We mentioned the harm condensation could cause, but you might not know that condensation is not always visible. If your bathroom walls are painted with a porous product, the water droplets could be absorbed into the wall.

You won’t see water dripping from the ceiling or along the walls, but the paint on your walls or ceiling could start peeling or flaking. You may also notice cracks and swollen portions of paint. These are all signs that your bathroom needs proper ventilation.

6. Damp Linens

Another hidden sign of poor ventilation is moisture trapped in the fabrics. These could be the towels in your bathroom, the bathroom rugs, bathrobes, and so on. If you’re sure you’ve placed fresh linens in your bathroom, but they feel damp when you touch them, it could be that the moisture in the air seeped through the fibers.

7. Too Hot or Too Cold Bathroom

Lastly, temperature levels that are too cold or too hot compared to the rest of your home are also a sign of poor ventilation.

In summer, the humid air gets very hot, making your bathroom feel like a greenhouse. In winter, the opposite is true – your bathroom will feel glacial but still damp.

If you notice a lack of comfort in the bathroom compared to the other areas in your home, consider installing a proper venting system.

5 Venting Solutions For Bathrooms With No Outside Access

As you’ve noticed, venting your bathroom is crucial even if your local codes don’t specifically ask for a vent. Here are five solutions to consider if your bathroom doesn’t have outside access.

1. Add a Ceiling Vent

Ceiling vents that get the damp air out of your home through the roof are the most popular solution for bathrooms with no outside access.

This solution can benefit your ground-floor and upper-floor bathroom alike, but for a ground-floor bathroom, you might have to divert the duct and take it up the roof through a wall (unless you want it to go through the middle of whatever room you have above the bathroom).

Ceiling vents do an excellent job in removing the moisture and lingering odors, and most models also feature light attachments that can increase your bathroom’s brightness.

2. Vent Beneath the Floor

If a ceiling vent isn’t a solution – for instance, if the bathroom is under the stairs or if you live in an apartment building), you could consider venting beneath the floor. In this case, the plumbing vents run between the floor joists and take moisture out through a wall.

If you’re considering this solution, pay attention to where you mount the vent fan. For the best results, you should place it as high as possible on a wall because the warm, moist air tends to rise. A vent located too low won’t be able to capture the moisture, and you’ll still have troubles with condensation and mold.

Connect the fan to the under-floor ducts through a vertical duct running through the bathroom’s wall.

3. Add a Recirculating Fan

Do you have a half-bathroom or guest bathroom that only has a toilet and sink but no tub or shower? You could fix the bad odor problem with a recirculating fan.

Recirculating fans aren’t necessarily vented, and you can install them on the ceiling or on the wall (some models are even freestanding). A filter inside the fan traps the bad odors and expels the air back into the room.

As you can expect, these fans won’t remove moisture. That’s why they only work in areas that aren’t really damp, such as a half-bathroom.

4. Expand Your Bathroom Ducts

If you already have a fan in your bathroom, but the space is still damp and musty, perhaps the fan or ductwork is insufficient.

Expanding your bathroom ducts means installing larger ductwork that can handle a higher airflow. Alongside the ductwork, you should also change the bathroom fan with a bigger one if the one you have is too small.

If you don’t know where to start, keep in mind that bathroom fans are rated for the amount of air they can move, and you need to move at least one cubic foot of air per minute for each square foot your bathroom has.

In other words, a 6’ by 9’ bathroom requires a fan of at least 54 CFM (the bathroom has 54 square feet). To stay on the safe side, you should round up the number and get a 60 CFM fan. Calculate your bathroom’s square footage and see what size fan you need, keeping in mind that the minimum you should get is 50 CFM (even if your bathroom is smaller).

5. Install Commercial Ductwork

Commercial ductwork is generally installed in apartment buildings, linking more bathrooms to the same large-diameter duct. However, you can install commercial ductwork in your house, too, routing the dampness in your bathroom out through a wall.

More often than not, exposed commercial ductwork can have a utilitarian and design function in one. This is often the case in industrial interiors where the exposed vent duct gains aesthetic value and becomes a focal point on your ceilings.

If you don’t like its appearance, you could always run the duct through a soffit or build a drop ceiling to hide it.

Frequently Asked Questions

You may now know how to vent a bathroom with no outside access, but you may still have questions. Check out the answers below.

How much does it cost to vent a bathroom fan outside?

Venting a bathroom with no outside access can cost you anywhere between $150 and $350, depending on what floor your bathroom is located, where you live, and the actual time required to do the job. However, this cost generally refers to adding a ceiling vent alone.

If you also require ductwork, the costs can go up to £3,000, and you may also need a permit from your local building department.

Is it OK to have a bathroom fan vent into the attic?

No, you should never vent a bathroom fan into the attic or in a soffit. The damp air should be expelled outside of the home, either through a roof or wall vent.

By venting into the attic, all you do is conduct the moisture from the bathroom into the attic. Instead of damaging your bathroom, all that dampness will start to damage the wooden structure of the attic, and the moisture could even seep into the walls.

Over time, this would lead to extensive rot and compromised structural stability of the roof and, perhaps, of your walls.

Because it’s unlikely that you will check your attic in time to spot the damage, expect very expensive restoration works. Not to mention that mold, mildew, and bacterial growth would still be a problem. That’s why you should only vent your bathroom to the outside.

Do I need a separate vent for each bathroom fan?

Yes, you generally need a separate vent for each bathroom fan. The only exception is commercial ductwork, but you should still consult the codes in your area and make sure that using the same duct for two or more vents is allowed.

Final Thoughts

Venting a bathroom with no outside access doesn’t have to be daunting. No matter where you live, you will likely find the perfect solution for you listed above. Now, all you have to do is to contact your city’s permitting office or a contractor in your area to get the project started.