Can Bathroom Fan Vent Into Attic? Avoid This!

You bought a new home, and as you went through a home inspection, you got into the attic. And hey! You noticed the smell, moisture and heap of mould on the roof rafters of the bathrooms. After a thorough inspection, you discovered that the previous homeowners vented their exhaust fans into the attic, not outside. So you are now asking yourself, Can Bathroom Fan Vent Into Attic?  

You cannot vent a bathroom exhaust fan directly into the attic. It would help if you never exhausted your bathroom fans in the attic because the place is not a temperature-controlled environment. 

The temperature inside an attic is generally not the same as that of your living space; it’s mostly closer to the outside temperature. This means that when the weather is cold, the vented air and its moisture will mix with the attic air causing condensation to form due to moist air from the bathroom. And it doesn’t have to be very cold below this can occur; once the temperature falls below the dewpoint, the moisture leads to the formation of water droplets on the roof rafters, the drywall and ceiling joists. 

As this happens, mould will start to grow to cause the rafters and ceiling joists to rot and possibly collapse from the roof weight. 

The best thing to do is to allow your exhaust fans to vent outside the house with no leaks in the interior of your house. Ensure your exhaust fans are done properly. This is achieved by following the building codes, which stipulate you provide your exhaust fan with a path to the outside of the house. This can be done by installing a roof vent or a capped vent to the side of your house. 

Why Do I Need A Bathroom Exhaust Fan?

It would help if you had a good bathroom exhaust fan to help the humid air from your bathroom leave your house directly without mixing with the air in the walls or attic causing condensation and mould. 

If you allow the air from your exhaust fan to mix with the air in the attic, which is mostly the same as the outside temperature, it can cause condensation, which will wet your rafters allowing mould to grow and, over time, weakening the structures of your home and posing health risks to you and your family. 

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It is good you know that venting bathroom exhaust fans outside isn’t enough; you must ensure it is venting properly. 

Where Should I Vent My Bathroom Exhaust Fans Then?

You might be wondering since I can’t vent my bathroom exhaust fans into the attic, where should I vent them?

The best way to vent your exhaust fans is to give it its direct vent to the outside of your house and not into the attic where it can mix with interior the air, causing the above issues.

Can I Vent My Bathroom Exhaust Fans Into the Soffit Vents? 

No. It’s not advisable to vent your bathroom exhaust fans into the soffit vents. 

If your exhaust fans are vented too close to the soffit vent (they are vented plates under the outer edge and roof of your home), the air can be sucked back into your attics from the soffit. 

Also, if your bathroom exhaust fans are vented too close to the soffit vents, they will get drawn back into the attic and form moisture which will also cause tissues above.

Can I Vent My Bathroom Fan into the Plumbing Vent? 

No, please don’t ever try venting your bathroom fans into the plumbing vent. This will vent sewer gases into your home, which are very explosive. Also, it can lead to an unpleasant and unhealthy smell.

Moreover, a drain vent is generally too small and humid to properly vent bathroom exhaust fans. Most bathroom fans were designed to vent through a 4″ duct, and a drain vent is usually 1.5″. This means if your exhaust fan pushes out any dust, it can accumulate inside the drain vent pipe, possibly blocking or slowing the drainage and the ventilation. 

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Also, you will have an obvious issue that anyone inspecting the attic will notice. You should make sure you install a larger sized duct with direct roof ventilation and avoid impacting your plumbing vent.

How Do I Vent My Bathroom If I Don’t Have Access to the Outside? 

If you don’t have access to the outside and need to vent your bathroom, don’t fret. We’ve options for you. You can create proper ventilation for your bathroom using one of these methods:

Using a Ceiling Vent

Installing a ceiling vent is one of the easiest ways to ventilate a bathroom that doesn’t have access to the outside. 

A ceiling vent is a machine that allows air to escape from your bathroom. It works by opening like a window and allowing the air to escape your bathroom.

Installing a ceiling vent ensures your bathroom doesn’t stay humid or moist. If you cannot do it yourself, consider hiring a professional to do it for you. 

Using a Floor Duct Vent

If your bathroom is located away from the exterior wall, it can be hard to vent it through the roof. This is mostly experienced by bathrooms built beneath a stairwell. 

When you have a bathroom that doesn’t have access to the outside and ceiling venting isn’t possible, you can use duct vents to ventilate it. 

A floor duct vent is a unique machine that uses floor grates to remove moisture and bad air from bathrooms. It provides additional exit points for odours and reduces moisture from the bathroom. 

Though floor ducts are effective,  ceiling ducts are considered more efficient and effective to them. 

Venting Through the Joist

This method is similar to venting through the ceiling. Instead of using a complex ductwork system, you will cut a hole in the first-floor joist cavity to vent your bathroom air outside. This is a cheap and effective way of venting the air in your bathroom to the outside.

However, it is very difficult to install the vents through the joist cavity as they are mostly cramped and difficult to work in spaces. You may also come across pipes and other obstructions to work around to get your ductwork done.

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Using a Recirculating Fan

A recirculating fan is also an effective way of drying up the air in your bathroom. However, it doesn’t exhaust air to the outside. Rather, it purifies the air in the bathroom via a filter and ensures all odours are eliminated. 

If you have half baths, recirculating fans are an excellent choice since you have no installed showers, and the moisture level is low. 

What Do I Look For When Selecting a Bathroom Fan?

Using a bathroom exhaust fan helps in preventing mildew problems and maintaining a healthier indoor air. Here are three things to consider when choosing a bathroom fan:

The Size of the Fan

Selecting the right size for your square bathroom footage ensures your bathroom is well ventilated. Exhaust fans are mostly sized and rated according to their ability to move air in cubic feet per minute (CFM)

Smaller and less powerful exhaust fans are ideal for tiny bathrooms, while larger fans with higher CFM are perfect for large bathrooms. 

Installation of the Fan

Most bathroom exhaust fans are installed on the ceiling, while few are installed on the walls. They come with integrated duct adapters that connect to the main ductwork of the house. 

Venting your exhaust fan air into the attic will only transfer warm and moist air to other areas of your home, which can still lead to moisture issues. When buying a new bathroom fan, consider where you want to install it, whether ceiling or wall. 

Noise Level

You can’t have a bathroom fan that sounds like a jet engine. It will rob your bathroom of its peace. 

Bathroom fan sounds are rated in Sones. One Sone is equal to the humming of your kitchen refrigerators which isn’t that bad. 

When choosing a bathroom exhaust fan, go for quieter models like the Broan Very Quiet Ceiling Bathroom Exhaust Fan.

Why is Ventilation Important?

Proper ventilation helps in removing excess moisture in the air, which can lead to air pollutants and end up affecting our health. 

Keeping your home well ventilated ensures you enjoy proper air quality, stay healthy and keep your home structure well-integrated for years.

Where Do Bathroom Fans Vent into?

Bathroom fans usually vent outside rather than the attic or ceiling. Venting your exhaust fans anywhere apart from outside poses the risk of condensation and mould forming. 

How Far Can a Bathroom Fan Be Vented?

Mostly, a 4-inch flex duct can be used to carry a bath fan for up to 25ft which is what is required by most codes. 

Can You Use a PVC to Vent a Bathroom Fan?

Yes, PVC piping can be used to vent a bath fan because it provides a better seal than metals, and it hardly leaks.