Bathroom Vent: Soffit vs. Roof (Detailed Comparison) | HomeCareHow.com (2022)

Installing a bathroom fan comes with one huge dilemma: should you vent it through the roof or through the soffit? The soffit sounds more approachable, especially if you want to install the vent yourself. But is it really the best choice?

When deciding between a bathroom vent through the soffit or roof, keep in mind that soffit vents can have a lot of problems. Installing a roof vent requires more skills, but it’s the appropriate choice for taking moisture and eventual sewer gas leaks out of your home.

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4 Bathroom Exhaust Fan Venting Options

There are several venting options when installing bathroom fans; however, some are more effective than others. Let’s have a look at them.

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Roof Venting

One of the most popular venting options, roof venting, takes the moisture and fumes outside of your house through the roof.

This venting system is relatively challenging to install because it could leak if installed incorrectly. However, this system is the best option if you want to prevent humidity problems inside your bathroom and home (moisture and heat rise naturally, so this venting type aids them to escape your house).

A disadvantage is that snow, fallen leaves, and bird nests could clog it.

Ceiling to Wall Venting

This venting option uses the same principle as the roof one, but a horizontal duct connects the fan with a vent hole located in the wall, near the ceiling.

This installation is preferred when you can’t use a roof vent for some reason – for instance, if you live on a lower floor in an apartment building.

The main advantage of the ceiling-to-wall venting is that it doesn’t leak as fast as a roof vent, but rain could still get inside and leak along the wall if the vent isn’t installed properly.

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Wall Venting

One of the simplest setups, a wall fan and vent, is another type of installation used in apartments. Similar to the ceiling-to-wall vents, these vents are less likely to leak compared to the roof type. Depending on the vent type, you’ll have to install the fan on an exterior wall or on any interior wall if you can route it through the ceiling or other walls.

Soffit Venting

Roof soffits are the underside portion of the roof that hangs over the walls. Soffits generally have a type of passive ventilation similar to ridge or gable vents.

Soffits have an important role in attic ventilation, but they aren’t exactly the first choice when it comes to exhaust fan venting. The main disadvantage is the fact that the cross-ventilation could conduct moisture and heat into your attic rather than outside.

Directing bathroom air into the soffit also requires more ductwork. Sure, there is no risk that the vent will leak, but there is a high probability it won’t work properly. If you really want to run the vent through the soffit, there is a way, though. More about this below.

Venting A Bathroom Fan Through The Wall

Venting through a wall – be it an interior wall, exterior wall, or directly through the roof – is the best bathroom venting solution. Either of these options will get rid of the moisture, heat, and fumes in your bathroom, leading them out of the house.

Pros of Venting through a Wall

Proper ventilation through a wall, ceiling, or roof will limit condensation in your bathroom and prevent mold and mildew growth. But there are other essential benefits of this venting type.

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  • Enhanced comfort: The increased effectiveness of wall or roof venting increases living comfort by reducing humidity levels. You can check the moisture level in your house with a digital hygrometer or smart home system to see how the bathroom fan can make a difference.
  • Better health: Lower humidity levels can help keep bacteria and mold at bay. These microorganisms can cause allergies or trigger asthma symptoms. Moreover, both mold and bacteria can cause various respiratory infections.
  • A more durable bathroom: Fewer condensation problems mean fewer problems in the bathroom. You won’t have to repaint as often, nor will you have to change the fittings and accessories too often. If you have hardwood floors, a proper exhaust fan and venting system can also protect them.
  • Less noise: Properly routed vents are definitely quieter compared to soffit venting systems. If you’re not fond of loud fan noises, this solution could be right for you.

Cons of Venting through a Wall

Perhaps the main disadvantage of roof and wall vents is that they can leak if installed improperly. Birds often build their nests in the exhaust fan vents, and wind can also send lots of debris straight in. Rain could also make its way through the vents straight into your bathroom.

Venting A Bathroom Fan Through Soffit

Venting through a soffit could seem like a good idea if you don’t want to make holes in your roof or walls. However, soffit venting is problematic and banned in some states. You should check your local regulations before even thinking about a soffit vent.

Pros of Venting through Soffit

Like wall or roof vents, soffit vents have advantages of their own. In addition to the installation ease, they are less likely to get clogged.

  • Easy installation: Soffit vents are easier to install compared to wall or roof vents. This project is more approachable for most DIYers, but remember that soffit vents aren’t legal in all states. Check the local laws before venting the bathroom fan through the soffit, or you could risk a fine.
  • No leaking problems: Soffit vents don’t open on the outside of your house, but in an enclosed space between the ceiling and the attic. Thus, you don’t have to worry about any leaking problems.
  • Fewer blockages: Just like rain can’t make its way to the vent, birds and debris can’t make their way either. Soffit vents are less likely to clog and easier to clean.

Cons of Venting through Soffit

The main disadvantage of soffit vents is that they might not work. The soffit has static ventilation that helps recirculate the air in the attic. Thus, instead of sending the moisture, hot bathroom air, and fumes out of your home, it could send them straight into the attic.

Apart from mold and mildew, the extra humidity can also damage your attic’s wooden structure, and the moisture and fumes could eventually work their way back into the bathroom or other areas of your home.

Is It Better To Vent Bathroom Fan Through Roof Or Soffit?

You should always vent your bathroom fan through the roof or, if the roof is inaccessible, through a wall. Venting through the soffit is never a good idea.

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FAQs: Answers You Should Know

Now that we established how you should vent your bathroom let’s see the answers to some other common questions.

What is the best roof vent for a bathroom fan?

There are many bathroom roof vents you can buy, and which is the best depends on your circumstances. The main things to look for are proper covering and adequate sealing. Once installed, you should have to add additional sealant nor install additional coverings.

What is the code for venting a bathroom fan?

Toilet rooms and bathrooms, when not provided with natural ventilation, should be ventilated by an exhaust fan with a minimum of 50 CFM. The exhaust air should not be recirculated within the residence and must be exhausted directly to the outdoors through an appropriate roof or wall vent.

Do I need a separate vent for each bathroom fan?

Yes, each bathroom fan needs its own vent.

Summary

Soffit venting could sound tempting, but you should steer clear of it. Not only can it exhaust bathroom air back into your house, but it can lead to humidity problems in your attic as well. Roof venting might be harder to install by yourself, but it keeps your environment healthier and reduces bathroom maintenance costs.

So, what do you say? Which kind of vent system do you prefer? Tell us in a comment.

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FAQs

Is it OK to vent a bathroom fan through the soffit? ›

A bathroom fan can be vented through soffit so that the warm air from the bathroom comes out through it and goes outside. However, It is important to keep in mind it can not be vented into the soffit, as this will lead moisture back into the attic.

Is it better to vent bathroom fan through roof or wall? ›

The fan exhaust must vent directly to the exterior of the home. Do not put the vent termination in a roof overhang or soffit. Don't put it on a wall near or under a roof overhang. The moist air that's belched out by the fan can be sucked right up into the open soffit vents and be drawn into your attic.

Do you need roof vents if you have soffit vents? ›

A roof may need soffit vents if there is no other ventilation allowing for adequate air movement. However, if the attic space is properly sealed and insulated, there is no need for this type of ventilation. There is no question that a standard attic space should be vented.

Are soffit vents worth it? ›

Soffit helps your home achieve the right amount of airflow circulation without allowing moisture to accumulate around the beams and interior elements of your home. This ventilation is achieved through mini-holes or vents in the soffit. These vents make your home breathable and provide air circulation to your attic.

Is it better to vent bathroom fan through roof or soffit? ›

Whether it's new construction or a remodel, a bathroom vent should always vent through the roof instead of an eave, overhang, or soffit. The point of a bathroom exhaust vent, or any vent really, is to remove hot, moist air from the house.

Is it OK to vent a bathroom into the attic? ›

No, you should not vent a bathroom fan directly into an attic. The problem with venting into the attic is that the moisture-rich air may form droplets on the wood sheathing, insulation, rafters, and ceiling joists, leading to mold growth.

Does bathroom vent have to go through roof? ›

Bathroom fans should always vent outside rather than through the ceiling and into your attic. Venting your bathroom fan into a wall cavity or attic runs the risk of mold growth. Building codes require new homes to vent bathroom fans outside the house.

Do bathroom exhaust fans need to be vented outside? ›

Bathroom fan installation requires outside ventilation. If the fan isn't accessible through an attic, you'll need to vent through a sidewall of your house.

Can you have too much soffit vent? ›

You can't have too much soffit venting, but it's worth noting the minimum requirements. Usually, 4-in. by 16-in. soffit vents are rated for 26 sq.

What is the best ventilation for a roof? ›

In most cases, we recommend soffit vents for intake and a ridge vent for exhaust. For homes that cannot have a ridge vent, box vents are generally the second best option for exhaust. And for homes that cannot have soffit ventilation, you will find that fascia vents to be your second best bet.

How many soffit vents should you have? ›

How Many Soffit Vents Do I Need On My Home? Most professionals generally agree that you should have one square foot of ventilation per every 150 square feet of attic, but make sure to review your local building codes to ensure proper ventilation.

What is the best type of soffit vent? ›

The flat grill type of soffit vent is a better option. These vents allow for more airflow and prevent problems like mold growth and poor indoor air quality that can occur with traditional slotted vents because they are open all year round.

Should soffit vents be covered with insulation? ›

You should not cover soffit vents with insulation, as this will prevent the air from flowing and could cause moisture damage to your insulation. Moisture can also build up behind the insulation and cause mold, which will only make your insulation less effective.

What type of soffit is best? ›

While there are a lot of materials on the market for soffits, only fiber cement resists moisture, insect activity, cracking, chipping, and fading. This makes it a better material overall for your home's exterior.

Where should bathroom fans vent? ›

Bathroom exhaust fans perform an important function by removing excess moisture from your home. When venting a bathroom exhaust fan, make sure to vent the air to the outside, rather than into your attic where it can cause mold and mildew to form.

Where do you put exhaust fan in bathroom? ›

You can place the fan directly over the bathtub or shower base, but it's sufficient to position it anywhere near the bathing area. If the bathroom has both a tub and shower, or a shower and a whirlpool tub, the fan should go somewhere between the two fixtures.

How far can a bathroom vent run? ›

Generally a 4 inch flex duct can carry a fan exhaust for up to 25 ft. Most codes require that.

How do you vent a bathroom with no outside access? ›

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.

Can I vent a bathroom fan through gable vent? ›

When venting a bathroom exhaust fan, make sure to vent the air to the outside, rather than into your attic where it can cause mold and mildew to form. Options for venting a bathroom exhaust fan include (best to worst): Through the roof or an exterior gable wall.

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

Venting through a wall with ducts costs $200 in labor, with $150 for the fan and parts for a total of $350. Venting directly outside through a wall costs between $130 and $600, depending on the wall's thickness, cut complexity, and size.

What is the code for bathroom ventilation? ›

Section R303.

When this section is adopted by a community, it essentially says that, for venting purposes, bathrooms must have windows that open. The code reads that the window must have "aggregate glazing area...of not less than 3 square feet (0.3 m2), one-half of which must be openable."

Does a ductless bathroom fan remove moisture? ›

Ductless exhaust fans have a charcoal filter system, allowing them to remove moisture from the air as well as mitigate odors.

How can I improve my bathroom ventilation without windows? ›

Here are a few solutions.
  1. Purchase an Exhaust Fan. Extractor or exhaust fans are the most common method of ventilating a windowless bathroom. ...
  2. Install a Fresh Air Supply Vent. ...
  3. Exhaust Fan + Air Supply Vent. ...
  4. Use a Dehumidifier. ...
  5. Install a Ceiling Fan. ...
  6. Install an Air Conditioner. ...
  7. Keep the Bathroom Door Open. ...
  8. Use a Regular Fan.

Can plumbing vents terminate in the attic? ›

Yes, a plumbing vent can terminate in the attic. But it must have an air admittance valve at the termination to keep noxious sewer gas fumes from rising into the attic.

Does a vent pipe have to go straight up? ›

Do Plumbing Vent Pipes Need to be Straight? Plumbing vents need to be straight on the vertical. This is necessary to avoid any vapor locks from occurring. When there is a bend in the vent pipe, moisture accumulates and is trapped.

How far should a plumbing vent stick out of the roof? ›

The International Plumbing Code (IPC), requires plumbing vent pipes to extend vertically at least 152 mm (6 in.) above a roof, per Section 905.5, "Vent Connections and Grades." Additionally, vent pipes must be at least 305 mm (12 in.)

Can 2 bathroom fans share a vent? ›

Bathroom fans can share a common vent. Both fans must be of similar capacity and have back-draft dampers installed. The duct must be over-sized by one inch for every additional fan added to the system.

How far does a bathroom vent need to be from a window? ›

It's best practice, then, to terminate your bath exhaust fan 3 feet from an operable window if you can do so.

Can I tie two bath exhaust fan vents together? ›

If you have two bathrooms that are close together and one has an exhaust fan and the other doesn't, you might be wondering if you can tie a new exhaust duct into the existing one. Well, you can't! You'd often blow air from one bathroom into the other, and local building inspectors wouldn't approve it.

How do you vent through soffit? ›

How to Install Soffit Vents
  1. Step 1: Make Two Parallel Lines. ...
  2. Step 2: Cut Parallel Lines. ...
  3. Step 3: Connect the Two Cuts. ...
  4. Step 4: Raise the Vent up to the Soffit. ...
  5. Step 5: Attach the Vent to the Soffit. ...
  6. Step 6: Remove Any Insulation From the New Vent. ...
  7. Step 7: Install the Ventilation Baffle.

Should bathroom exhaust fans be vented outside? ›

Note that the bathroom vent fan must always exhaust to the outdoors; never allow the duct to simply blow into an attic, crawlspace or other enclosed area.

Do all bathroom fans need to be vented outside? ›

Bathroom fan installation requires outside ventilation. If the fan isn't accessible through an attic, you'll need to vent through a sidewall of your house. These types of ducts and vents are typically installed when the house is built. If you don't have a duct leading to a sidewall vent, call a professional for help.

Can you vent a bathroom fan through an existing roof vent? ›

Venting your bathroom fan might seem like an easy do-it-yourself project, but we don't recommend it. First, inexperienced homeowners might accidentally vent the exhaust fan through an existing roof vent or even into the attic.

How do you run a bathroom vent through soffit? ›

How To Vent A Bathroom Fan Through A Soffit (4-Step Guide)
  1. Install The Duct As Straight As Possible.
  2. Use The Right Sized Duct For Your Exhaust Fan.
  3. Cut The Soffit Hole In The Right Location.
  4. Connect The Bath Fan Duct To The Soffit Cover.

Can you have too much soffit ventilation? ›

You can't have too much soffit venting, but it's worth noting the minimum requirements. Usually, 4-in. by 16-in. soffit vents are rated for 26 sq.

How many soffit vents do you need? ›

How Many Soffit Vents Do I Need On My Home? Most professionals generally agree that you should have one square foot of ventilation per every 150 square feet of attic, but make sure to review your local building codes to ensure proper ventilation.

What is the code for bathroom ventilation? ›

Section R303.

When this section is adopted by a community, it essentially says that, for venting purposes, bathrooms must have windows that open. The code reads that the window must have "aggregate glazing area...of not less than 3 square feet (0.3 m2), one-half of which must be openable."

Can you vent a bathroom fan through side of house? ›

Can a Bathroom Fan Vent through a Side Wall? You can vent your bathroom fan through a side wall of your house. A side wall is your best option when you don't have access to the eaves of your home and don't want to go through the roof.

What is the point of a ductless bathroom fan? ›

Ductless exhaust fans have a charcoal filter system, allowing them to remove moisture from the air as well as mitigate odors. They can be attached to the wall or ceiling and are a quiet and energy efficient ventilation solution.

How do I stop moisture in my bathroom without a fan? ›

If your bathroom doesn't have a fan, take advantage of the door and window(s) to let out steam. Whenever weather permits, open the window during your shower or bath and leave the window open for at least 15 minutes after you exit.

Can two bathroom fans share a vent? ›

Bathroom fans can share a common vent. Both fans must be of similar capacity and have back-draft dampers installed. The duct must be over-sized by one inch for every additional fan added to the system.

How far can a bathroom vent run? ›

Generally a 4 inch flex duct can carry a fan exhaust for up to 25 ft. Most codes require that.

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

Venting through a wall with ducts costs $200 in labor, with $150 for the fan and parts for a total of $350. Venting directly outside through a wall costs between $130 and $600, depending on the wall's thickness, cut complexity, and size.

How far does a bathroom vent need to be from a window? ›

It's best practice, then, to terminate your bath exhaust fan 3 feet from an operable window if you can do so.

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