What Is a Bathroom Fan For: Everything You Need to Know

What Is a Bathroom Fan For

A bathroom fan is an exhaust-type ventilation system that collects moisture and odors from your bathroom and moves them outside. This ventilation is necessary to prevent excess moisture, mold, and rot in your home. 

Unfortunately, for many older homes, bathroom fans are the only actual means of mechanical ventilation. That’s right. If you don’t have an air exchanger in your home but you do have a bathroom fan, chances are it is the only way to exhaust stale air from your home to the outdoors. It is essential to realize that bathroom fans function only as an exhaust fan. This means that your bathroom fan is not responsible for bringing fresh air into your home; it is only responsible for bringing ambient air from the bathroom to the outside. 

Therefore, using an air exchanger is still essential to get other forms of mechanical ventilation in your home. (Below) in this article, I will cover the benefits, the different types of bathroom fans, the cost of installation, and how to choose the right fan based on CFM and Sones. 

Related Tools that can measure indoor humidity

For more on tools that can measure indoor humidity read the full article.

The Key Benefit of a Bathroom Fan

The key benefit of a bathroom fan is primarily for your home’s health, as it manages humidity levels and eliminates odors. It is also good to know that high humidity levels create ideal conditions for pests such as cockroaches and dust mites. However, the biggest drawback of bathroom fans is that they are usually a retrofit option, which means you will have to create a new hole in the side of your home to use it. That plays against the airtightness of your home, and you’ll want to consult an experienced professional to do the job. 

Most bathroom fans serve the same function of getting rid of excessive odors, humidity levels, and even mold spores that build up in a damp bathroom environment. However, fans differ depending on where they are mounted, how they expel moisture and air inside bathrooms, and any extra features they may have. 

5 Different Types of Bathroom Fans

1. Ceiling Mounted

The most typical bathroom fan installation is ceiling-mounted. The fan is recessed inside a ceiling cavity, and its ducts lead outside the house. 

2. Wall Mounted

Wall-mounted bathroom fans are relatively common and are attached directly to an exterior wall. Some people complain that they can be more prone to drafts and don’t effectively capture moist rising air. 

3. Building Exterior Mounted

Building exterior-mounted bathroom fans are fans that, as the name implies, are mounted on the exterior of a building and are most common in commercial applications. 

4. In-Line

In-line bathroom fans are built-in and refer to whole-house systems such as HRVs and ERVs that replenish the bathroom air with fresh air to other rooms in the home. 

5. Smart & Lighting Features

Bathroom fans with light fixtures are versions that have built-in LED lighting, and some now even have Bluetooth speakers built-in if you want to be a tech geek. Some of the most recognized brands in this category are Panasonic, Delta, Nutone, and Broan. 

Related What exactly is a toilet trap and how does it work

For more on what exactly is a toilet trap and how does it work read the full article.

How to Choose the Right Bathroom Fan

When choosing a bathroom fan, the first thing to do is find the ideal one that fits the space. And the ideal way to find out is to look at two clear indicators: CFMs and Sones

Bathroom Fan CFM

Bathroom fans are rated by their CFM rating, which is their cubic feet per minute indicator, also known as the amount of air they can move in less than a minute. Generally, a more powerful fan will give better results. Still, you also don’t want to overpower your bathroom with a huge fan or pay more for an enormous one you might not need. And generally, the higher the CFM, the louder the fan will be. 

Now the quick and easy way to calculate the size of fan you need is with this simple math equation. And all you need are the approximate measurements of your bathroom. For example, let’s say a small bathroom 9×5 ft wide and 8 ft tall ceiling; you multiply those three numbers by 0.13. This will give you the minimum CFM rating required for that bathroom. You must also factor in the CFM loss for the amount of ductwork installed. Typically, you can calculate a 7% CFM loss for every 25 feet of flex duct and 3% for every 90-degree turn. 

Related Can shower heads save water

For more on can shower heads save water read the full article.

Bathroom Fan Sones

This is essentially the second indicator that tells you how loud your fan will be. And fans are usually below three Sones. This is tricky because while a lower Sones number means a quieter fan, there are fans that are very quiet regardless of their Sones number. Sometimes having a noisy fan, especially in bathrooms that guests often use, is doing a service to you and your visitors if you know what I mean. 

Labels to Look for on a Bathroom Fan

  • Energy Star label: Once you feel good about the CFM rating and Sone level, look for the Energy Star label. The efficiency requirements for bathroom fans are still pretty low to meet Energy Star standards. 
  • HVI label: The other is to look for an HVI label for the Home Ventilation Institute. This institute certifies home ventilation products, and for bathroom fans, it affirms that the manufacturer’s details are what they are, especially regarding CFMs, Sones, Wattage, and illumination. 

Related What is a 3-way dimmer switch

For more on what is a 3-way dimmer switch read the full article.

How Easy Is It to Install a Bathroom Fan

Now, when it comes to installing your bathroom fan, it can get pretty complicated pretty quickly. The ease of fan installation will depend mainly on the location of your bathroom within the house, whether there is an existing fan and ductwork, and whether or not there is wiring already in place or accessible. Now, a quick note on older homes with attic vent fans: Make sure the vent leads outside. I see a trend for older homes to have their exhaust stop in the attic rather than reach outside, which can cause many problems in the attic space. 

Related Do doors expand in summer

For more on do doors expand in summer read the full article.

How Much Does a Bathroom Fan Cost

There is a broad range of prices to choose from, but usually, for a small and efficient bathroom fan, you can get it for around $100 to $150. Now keep in mind that is just the price of the fan itself. You’ll need a licensed electrician to wire it up, install it, and vent it to the outside. You may also have to do some patching on the wall if you’re replacing an old unit, which again adds to the price. In the end, most of the price is actually in the installation and accounting for replacement parts such as exhaust ducts, wiring, and switch installations, which brings the cost of a bathroom fan installation closer to the $300 to $500 range for a fully operational fan. 

You can also do some things to save on the cost of running that fan in the future. Try to choose a model that, at a minimum, is Energy Star-rated. And going one step further, look for a fan with a high CFM per watt rating. Some models go as high as 19 CFM per watt, so try to find one with a rating of at least 10 CFM per watt. This means that the most efficient models use as much energy as a typical LED bulb. 

Related Is water heater an appliance

For more on is water heater an appliance read the full article.

Should You Leave the Bathroom Fan On

Never leave a bathroom fan on for too long because they tend to overheat and accumulate lint and dust over time, which could pose a fire hazard. But installing a timer switch is a great way to control your bathroom fan easily. Here’s the lowdown.

All bathrooms by building code are required to have a ventilation fan. The only exception is if the bathroom has a window to the outside that you can open. But even if the bathroom has a window, I suggest businesses and homeowners have a bathroom fan installed. So a bathroom fan, of course, as I mentioned above, is to ventilate the humidity in bathrooms, which is an essential function. And they’re usually connected to a normal two-pole on/off switch. 

On the low end, the bathroom fans operate at 50 cubic feet per minute, pulling about 50 cubic feet of air every minute. And that’s assuming you have a very short duct that it’s connected to. But the idea is that these fans only pull about 50 CFM, and that’s on the low end, and they can go up to 100 to 120 CFM on the really powerful ones. But again, that’s assuming it’s only pushing air a very short distance. 

We’re all familiar with those bathroom fans that make a lot of noise and sound like they’re doing something, but we never really feel the air moving. We know these fans barely draw any air, so what do we do? We turn them on, and they run while we’re in the bathroom, and then basically, they’re not accomplishing anything because when we come out of the bathroom, we turn off the fan. So the fan hasn’t pulled all the moisture out correctly because we haven’t given it the time it needs to do its job. 

The solution is to install a timer switch on the bathroom fan. I believe every business and homeowner should have one in every bathroom with a fan. After installing the timer switch, you can set the timer for a certain number of minutes when you leave the bathroom. The fan will run for those minutes and automatically shut off. And you don’t have to stand around holding the switch, turning it on, or letting it run for 20 minutes and then forget about it, which would result in the fan running all day, which isn’t a good thing. 

Related What is the purpose of a GFCI

For more on what is the purpose of a GFCI read the full article.

How Long Should You Run the Fan in the Bathroom

I’ve done some math to help you understand how long you should leave the bathroom fan running. For example, let’s say for an 8×15 ft bathroom, that would put it at 120 square feet of floor space, and if the bathroom has an 8 ft tall ceiling, you’re going to have a total of 960 cubic feet of air space in that bathroom. And if your fan is pulling at 50 cubic feet per minute, pulling all the air out of that 960 cubic feet of bathroom air space will take 20 minutes. Of course, you’re not going to stand there for 20 minutes while the fan blows the air out and then come back half an hour later and turn it off. It would be ideal if you had a way to make that fan turn off automatically. 

For another example, let’s say you have a more powerful fan that can pull about 100 CFM with the same 960 cubic feet of bathroom air; you are still looking at 10 minutes for the fan to pull that volume of air out. Now, if you have a 4×8 ft half-bathroom with an 8 ft tall ceiling, you will have about 250 cubic feet of air space in that bathroom, and a 50 CFM fan will still take about 5 minutes for the fan to pull the air out. So putting the bathroom fan on a timer is a better way to go. 

There are different timer switches, including the push button where you can push in a 5, 10, 15, or half-hour, which is excellent. The other type of timer has a mechanical dial that you turn manually clockwise. It is also known as an analog timer. The other type of timer is a smart switch that you can program to run at a specific time desired. 

Can Bathroom Fans Affect the Environment

Generally, products in this category, regardless of the manufacturer, tend to be very similar regarding the materials used and their origin. Most of these fans are made from molded plastic and lightweight steel. Therefore, they are not overly innovative and, for the most part, take a bit of energy and resources to create. 

Most of these products are made overseas, but if you can find a version made in the USA, it’s a great way to reduce the footprint. Also, choosing a version with high CFMs per watt, at least ten or more, is another excellent way to reduce the impact of your daily use, which will also translate into savings for you. 

Related A guide to drywall do’s and don’ts

For more on a guide to drywall do’s and don’ts read the full article.