Why Bathroom Fan Doesn’t Vent To The Outside? Troubleshooting Guide

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Bathroom fans are excellent for removing moist air from your bathroom and maintaining good ventilation. However, they can only perform well when they vent outside your building. So, what stops the bathroom fan from doing that?

Your bathroom fan doesn’t vent to the outside because the fan blade is damaged or the motor is faulty. When that happens, no airflow can be generated at all. Besides that, long vent ducts or those that are bent, kinked, pinched, or clogged with dirt, will restrict airflow and stop your bathroom fan from venting outside.

Keep reading through this guide to discover how to troubleshoot your bathroom fan, identify its problems, and fix them yourself.

Why Isn’t My Bathroom Fan Venting Air To The Outside?

When the air from your bathroom fan doesn’t flow to the outside, troubleshoot the unit for these problems:

Fan Blade Or Motor Problems

About this: The bathroom fan’s motor drives the air from the bathroom through the vent. The motor does that by spinning a fan blade (or blower wheel) with fins that move air as they turn.

The fan motor and blade must be in excellent condition to ensure maximum airflow through the vent and outside the building.

What’s wrong: The first reason to consider when your bathroom fan doesn’t vent outside is a problem with the fan motor or its fan blade.

Remember: without these two components functioning correctly, air can’t flow through the bathroom fan’s unit.

For example, the fan blade could be damaged from misalignment. A misaligned fan blade will grind against the inside of its housing, eventually causing one or more fins to break. When that happens, it loses its ability to move air. 

Besides, the fan motor could have failed due to excess wear or a short circuit. That will prevent the fan from turning the fan blade, preventing airflow.

How to fix it: First, inspect the fan motor and blade to ensure it’s in optimal condition. Fan blades must be replaced with new ones if they’re broken.

Unfortunately, that’s also true for the fan motor. Worn-out or shorted fan motors can’t be serviced, so you’ll have to dispose of the one you have and install a replacement.

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Read: What Is Bathroom Fan Sound Rating?

Vent Ducts Are Too Long

About this: While the fan unit sits in the bathroom and draws air out, the vent ducts help move that air outside the building.

Some homes have rigid ducts, which cost more but are safe from being kinked or pinched by anything that might fall on top of them.

Meanwhile, others use flexible ducts that are more affordable and flexible. But, unfortunately, those are easily bent too far or affected by falling objects.

Whether rigid or flexible, these vents must be as straight and short as possible to ensure the air reaches outside the building.

What’s wrong: Your bathroom fan won’t vent to the outside if the ducts it uses are too long.

Remember: your bathroom fan unit’s motor and blade are small and not designed for heavy-duty use. As a result, they can’t drive air through long lengths of ducting.

Instead, they’ll remove the air from your bathroom only to have it stuck inside the duct, not reaching the outside.

How to fix it: You can solve this problem by ensuring that the vent ducts you use are as short as possible. The goal is to give the air the shortest distance possible to escape the building.

Ideally, that would mean venting out through the nearest wall. Alternatively, you could vent the bathroom fan through the roof if that’s the shortest distance to the outside.

Read: Why Nutone Bathroom Fan And Light Stopped Working? – Troubleshooting Guide

Vent Ducts Are Kinked, Bent, Or Too Small

About this: As you read above, the vent ducts for your bathroom fan must be as short and as straight as possible. Naturally, some minor bends are unavoidable. But as long as there aren’t too many, and those bends aren’t excessively sharp, airflow will be smooth.

Besides that, the sizing of those vents also matters. The vent duct’s size must match the power of your bathroom fan motor to ensure that it can cope with the amount of air being pushed through.

When that’s the case, you can rest assured that the air will vent outside without any problems.

What’s wrong: The condition of the bathroom fan vent ducts is another likely reason the air isn’t venting to the outside.

Firstly, the ducts might have too many bends or bends that are far too sharp to maintain smooth airflow. On top of that, the duct might also be pinched when squeezed between narrow spaces or because an object has fallen onto it.

Lastly, the size of the vent might be too small. When that’s the case, it won’t have enough capacity or room for all the air blown in by the bathroom fan motor that’s too large. 

That typically happens when upgrading to a more powerful bathroom fan but not investing in a larger vent duct to match it.

How to fix it: Firstly, check your vent ducts to free them from any kinks or bends. Remember to keep them as straight as possible to maximize airflow.

If that’s still not enough, or if you’ve recently upgraded your bathroom fan, you should switch your vent ducts for larger ones.

Follow the bathroom fan manufacturer’s recommendations for vent sizing, as they’re sure to include that information with your purchase.

Dirty Or Blocked Ducts

About this: Your vent ducts must also be clean to ensure optimal airflow.

Although it’s easy to overlook the vent ducts, you must remember that they can quickly accumulate dust and other debris.

Aside from the indoor portion, the external flap where the vent terminates can also let outside dirt into the vent if it doesn’t close correctly.

What’s wrong: The final reason your bathroom fan doesn’t vent outside is the vent is too dirty or clogged. Buildups of dirt and other debris will restrict airflow. When those buildups get too severe, no air can flow through the duct.

As a result, the bathroom fan won’t vent, and the air will remain stuffy.

How to fix it: You can fix this by cleaning your dirty or blocked vent ducts thoroughly and regularly. Detach the vent to clean its inside with a vacuum and a brush.

Alternatively, you can also clean the vent from outside using a telescopic brush, similar to how you’d clean your dryer vents.

Frequently Asked Questions (FAQs)

Check out these frequently asked questions and answers to help you troubleshoot your bathroom fan:

Do Bathroom Exhaust Fans Need To Be Vented Outside?

Yes, bathroom exhaust fans must be vented outside. That way, the moisture and dirt that the air carries can be removed from your bathroom straight to your home’s exterior.

How Should Bathroom Fans Be Vented?

Ideally, bathroom fans should be vented through the closest wall directly to the outside. However, if that’s impossible, you can vent it through the ceiling and out the roof instead. Whatever you choose to do, keep the vents as short and straight as possible to maximize airflow.

What Is The Point Of A Ductless Bathroom Fan?

Ductless bathroom fans typically rely on charcoal to remove moisture and odors from the air it draws through. However, that is less effective for maintaining ventilation than a fan that vents to the outside.

Should I Close The Door When Using A Bathroom Fan?

You can close your door when using a bathroom fan if the door has enough of a gap to allow air to flow in. If not, you’ll have to open your door slightly to let fresh air flow into the bathroom as the fan draws out moist air.

What Ducting Is Best For Bathroom Fans?

Ideally, round ducting is best for bathroom fans as it maximizes airflow. However, you should use whichever ducting is best for your home’s architecture.

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