Are Bathroom Fans Interchangeable

Are Bathroom Fans Interchangeable? 6 Things To Know

In Home Maintenance by Giovanni ValleLeave a Comment

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Do you feel that your bathroom fan has lost its venting power and see mildew appearing on the ceilings and walls? Maybe it’s time to change the fan and go for a more powerful one. But are bathroom fans interchangeable?

Bathroom fans are interchangeable so long as you replace your fan with one of the same size and type. You should consider the fan’s ability to move air expressed in CFM (cubic feet per minute), duct length and size, housing size, sound, and features like humidity sensors.

Keep reading to learn more about the considerations to keep in mind when changing bathroom fans.

6 Things You Should Know Before Changing a Bathroom Fan

When changing out a bathroom fan, you need to consider a few things to ensure you get a new one that’s interchangeable with the old one.

1. Your Old and New Fan Housing Must Be Similar in Size

The size of the bathroom exhaust fan is the first thing you should consider when you want to change it. When you want to swap your existing fan with a new one, make sure they’re the same size, or you’ll run into trouble housing the new fan.

Another size-related consideration is the cutout dimensions, the hole in the ceiling or wall where you mount the fan. That’s the first thing you should measure before choosing the new fan by removing the fan cover and measuring the dimensions of the opening.

That said, if you don’t find a fan that’s a complete fit for the cutout dimensions, it’s better to find a fan slightly larger than the wall or ceiling opening. This way, you can cut the drywall to fit the new unit.

If the fan size doesn’t fit the old fan’s housing, you may need to remove some tiles to make room for it. That’s not what you want as it opens a can of worms and is easily avoidable by choosing the right size fan.

2. The Duct’s Length and Size Depend on the Bathroom

The ducting is another major thing to consider as it can limit your choice of fan. The duct is the pipe that removes the air from the fan through the ceiling outside. Unless your old ducting is damaged or the new fan requires new ducting, you don’t need to change the ducting.

The duct’s length and size will depend on the bathroom size, the fan size, and the distance from the bathroom to the outside vent.

There are different duct sizes, including 4” (10.16 cm), 5” (12.7 cm), and 6-inch (15.24 cm) round types. Typically, a 4-inch (10.16 cm) round duct will work for a 50 CFM (84.95 m³/h) fan, and bigger fans need 5-inch (12.7 cm) or 6-inch (15.24 cm) round ducts. That said, you can also use duct adaptors to adjust your duct size to the fan.

The best way to figure out the best duct size and length is to look at the requirements that come with the fan. Improper duct size may force too much air in the duct, leading to insufficient extracting and pressure on the fan.

3. You Can’t Eliminate Noise From a High-Powered Fan

Having a noisy fan can be a real turn-off when trying to extract humidity out of your bathroom. It may be the only reason you try to change your old bathroom fan. A fan’s noise is measured in sones. The older the fan, the louder the noise. Newer fans have noises measuring less than one sones.

However, the more high-powered the fan, the noisier it can get, and there’s nothing to do about it. Moving air makes noise even if the fan’s motor is quiet.

But you can look for lower sones to minimize noise. For example, the Panasonic WhisperSense DC Ventilation Fan available on is highly efficient and reliable with 0.3 sones. It also has an integrated moisture sensor that automatically turns the fan on and off.

4. Fans With High CFM Ratings Are Best for Larger Bathrooms

One of the most important features of an exhaust fan is its ability to vent air out. Cubic feet per minute indicate the maximum air the fan can take out of the bathroom at its highest capacity.

If your bathroom is large, opt for a fan with a high CFM rating. A rule of thumb is that you need 1 CFM (1.69 m³/h) per square foot (0.09 sq m). However, the minimum amount of CFM is 50 (84.95 m³/h), meaning even if your bathroom is smaller than 50 square feet (4.64 sq m), you can’t go for a lower CFM.

That’s ok since it’s always a good idea to go a little over the calculated measurements. For example, if your bathroom is 55 square feet (5.10 sq m), getting a fan with a CFM of 60 (101.94 m³/h) is better. A higher CFM allows you to take a hot shower and have the bathroom dried in less than 5 minutes to avoid mildew.

For bathrooms larger than 100 square feet (9.29 sq m), other factors come into play in calculating the fan size: the number of fixtures. For instance, if you have a bathtub in your bathroom, you’ll need a fan of 50 CFM (84.95 m³/h).

Here are the fixture requirements:

  • Shower: 50 CFM (84.95 m³/h)
  • Bathtub: 50 CFM (84.95 m³/h)
  • Toilet: 50 CFM (84.95 m³/h)
  • Jetted Tub: 100 CFM (169.9 m³/h)

In addition to these measurements, you may also want to get a second fan. For example, if you have an enclosed showering area separated by doors, it’s better to have another fan for that area. It also helps to pick a fan with two different speeds and powers to adjust them when you need to.

5. Different Bathroom Sizes Call for Different Exhaust Fans

Unless you choose to go for a bathroom fan the same as the previous one, it helps to know other bathroom fans. This way, you can choose the best exhaust fan with optimal venting capacities for your space.

The two most common types of exhaust fans are:

  • Centrifugal: These fans can extract air from a long distance, thanks to their long ducting designs. They’re best installed on ceilings and can be noisy.
  • Axial: These fans are better for wall mounting because they can’t move air over long distances. So, they directly remove air through an external wall.
  • Inline: They’re perfect for very long distances between the bathroom and outside vents. They pass through several ventilation layers and are very quiet.
6. Extra Features Are Worth It for Better Fan Efficiency

If you want to retrofit, you can find new fans with added features that increase the efficiency of your exhaust fan.

Some exhaust fans come with humidity sensors that automatically detect humidity and turn the fan on and off when needed. For example, this Delta Electronics (Americas) Humidity Sensor Fan that you can get on is one of the best fans available on the market that comes in different CFM sizes.

Another extra option is lighting that can increase your bathroom’s lighting levels or serve as the only light source in your space. Some of them, such as Delta Electronics (Americas) Fan/Dimmable LED Light on, also have dimmable LED lights that allow you to adjust the lighting.

You could also find bathroom fans with heaters that can heat your bathroom, perfect for those chilly winter mornings. This way, you can combine the heat from the fan and the thermostat to create a warm, pleasant space for taking a shower or bath.

If you opt for these extra features, you may need to change the wall switches if your old fan was basic.

And the most vital thing to remember is that you should hire a professional to do the wiring and electrical work if you haven’t done it already. Plus, you need to check your local building codes and see if you’re allowed to do the wiring yourself.


Bathroom fans are interchangeable, and you can swap your old one with a new fan with more powerful features.

If you opt for a fan of the same type as your old one, you don’t need to consider other features. But if you want an upgrade, here are the things to consider:

  • Fan size
  • Ducting
  • Housing
  • Noise

Other features such as heating, humidity sensor, and lighting can help you get better performance.

Even if you opt for a basic fan, make sure to use a wall switch with a timer to set the time you want the fan to operate.


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