Why do I need a bathroom fan?

Bathrooms are excellent places to grow some of your home’s worst enemies: mold and mildew. Excess moisture in your bathroom (or other areas of your home) causes mold and mildew to grow. Mold and mildew only need oxygen, a food source, and moisture to grow. Mold and mildew can damage the fixtures of the bathroom such as the trim, drywall, paint, doors, and more because for the mold and mildew, these fixtures are a food source.

Most building codes now require a fan in every bathroom. Why? Because fans help ventilate the room, remove bad smells, and remove moisture. The most important function of the fan being to remove moisture. Even if the bathroom has a window, a fan is the best way to prevent moisture buildup.

Keeping your bathroom dry, well ventilated, and consistently using an exhaust fan is critical to preventing mold and mildew growth.

What size fan do I need?

Fans come in many different shapes and sizes, however, the size fan you need depends on the size of the room. Contractors are required by building codes to put in fans, but they may not be sized properly.

Check the CFM (Cubic Feet per Minute) rating of your fan to be sure it is the right size for your bathroom. This is usually marked on a label under the grill of the fan. A fan that has a rating of 50 CFM is suggested for bathrooms less than 50 square feet. For bathrooms more than 50 square feet, the recommendation is 1 CFM per square foot.

How do I measure the bathroom in cubic feet?

To measure the bathroom, you first measure the length and width of the room. If the bathroom has a more complex shape, measure in sections and add the areas together. For a bathroom that has ordinary ceiling height (8-10ft), you can simply use the area to determine the CFM. As a general rule of thumb, for a room less than 100 square feet, you need 1CFM per square foot. So if the bathroom is 10 feet by 7 feet your square footage would be 70 feet and you would need a fan that has a CFM of 70 or higher. Check out How to Choose The Best Bathroom Fan Size for Your Space to learn more.

How do I get people to use the fan?

That’s always the million dollar question! Kids, friends, family, and others visit your home, and will use the bathroom. How do you get them to use the fan? Here are 3 possible solutions:

1. Hard wire the fan to the same switch as the light. This will make the fan turn on every time someone enters the room. Although this is an easy fix, it means the lights will also stay on if you leave the fan on. It’s not the most energy efficient method.
2. Install a timer. When you are ready to bathe, simply turn on the timer, and the fan will automatically shut off at the designated time. Some timers (like this one from Amazon) have presets built in, so that you can have the fan, lights, or heater come on for a set amount of time. Timers can also help lower your energy bill by turning off the lights, fan, or heater at a set time. No more having to remind family members to turn out the light or the fan!
3. Install a fan with a moisture sensor. Every time the fan senses a certain threshold of humidity (greater than 40-50%) it would come on and automatically ventilate the area until the moisture level decreased below the threshold. These fans are the most expensive option, but also the most effective at keeping moisture thresholds low, which prevents mold growth.

Fans should be run during and for at least 20 minutes after showers are over. Running the fan lowers moisture levels and reduces mold and mildew growth.

What kind of fan should I buy?

The answer depends on several factors. Convenience, cost, and ease of installation being some of the top considerations. Knowing the people who will use the fan most may also influence the kind of fan and method of use.

Before beginning a search for a good quality bathroom fan, remember to measure the room. How many cubic feet is the bathroom? Be sure to choose a fan that has the correct CFM rating for your bathroom.

Before purchasing a new bathroom fan ask yourself these questions:

1. Who will use this bathroom? Is this a bathroom guests or children will use? Are the people who use this bathroom more or less likely to turn the fan on and off?
2. How much am I willing to spend on a good quality bathroom fan? Knowing your budget is key to choosing the best fan for the area. If you have a lower budget, a separate timer would be more cost effective than a more expensive fan with a moisture sensor.
3. How difficult/expensive is the fan to install? Do you plan to DIY and need a fan that is easy to put in yourself, OR do you plan to hire a contractor or handyman to do it? How much money/time are you willing to invest?
4. What kind of features are you looking for in a bathroom fan? Do you want an automatic timer or a moisture sensor? Do you want the fan to be easy to clean?
5. Is the fan working properly? What size do I need? Of course, before rushing out to buy a new fan, you should check the old fan, and see if it has the correct CFM rating.
6. What about fan maintenance? Is it clean? Eeeww! Dust! To keep fans clean and working properly, be sure to vacuum the grill often. You can even take the grill off, and wash it with soap and water to help it run more smoothly. Be sure to let the grill completely dry before reinstalling it.

To learn more about bathroom fans and to see the top rated fans of 2020 check out: 9 Best Bathroom Fans – (Reviews & Buying Guide 2020) by HomeAir.org.

Installing Bathroom Fans

If you are simply replacing a bathroom fan that is already present, reinstalling a bathroom fan is definitely something you could DIY.

However, if you are installing a new fan, where no fan was before, you will have to add a duct and cut a hole, either in the wall of the home or in the roof to vent the air to the outside of the building. We have seen many buildings with bathroom fans vented to the attic, but not outside the home. This is never a good idea! Most of the time, when this one critical piece of infrastructure is missing, the home develops mold in the ceiling and in the attic. Bathroom fans should always include a duct system that vents to the outside of your home.

Installing a completely new fan may require more work than you want as a DIY project. Check out How to Install a Bathroom Exhaust Fan from the Spruce to learn more.

No Mold Or Mildew For Me Thanks!

Remember, there are three big ways to prevent both mold and mildew from growing in your bathroom.

1. Keep it Dry – Moisture is key for fungal growth. Use the bathroom fan for a minimum of 20 minutes after showering. Keep doors and windows open when possible. Help towels get dry by hanging them horizontally and giving each towel plenty of space.
2. Renovate your bathroom to prevent moisture buildup. Install a bathroom vent fan that is the correct size for your room.
3. Keep it Clean – Use non-toxic cleaners to remove mold and mildew. To learn more check out our posts: Branch’s Non-Toxic Spring Cleaning Guide and How to Clean Mold.

These three simple steps can help keep mold and mildew at bay, and make your home cleaner and safer!

We’re Here When You Need Us

Call Branch Environmental. We’re experts not only at mold removal, but at determining and remediating the underlying causes. From hidden mold sources to major contaminants. We can identify exactly what is going on in your home and rid it of environmental toxins, often for good.