How Long To Leave Bathroom Fan On After Shower?

All of us understand the importance of a bathroom fan for ventilation in bathrooms. However, not all of us understand that turning off exhaust immediately can lead to unwanted outcomes. This is because the steam that has built up in shower rooms causes harm to the fan motor.

The Home Ventilation Institute suggests operating a bathroom fan for about 20 minutes after showering to remove steam from the bathroom and vent it out through the ducts. You can use a timer switch for the bathroom fan to ensure that it runs at the optimum duration.

But what is it about a bathroom that necessitates the need for the fan to keep running even after taking a shower? What’s the implication if there’s still steam in your bathroom ten minutes after the suggested time frame?

Is it ideal to operate a bathroom vent constantly for optimum moisture protection? In the sections that follow, we address your questions and provide you with answers.

The Recommended Ventilation Duration for a Bathroom Fan

For proper ventilation in the bathroom must undergo about eight air changes every hour; this is according to the Home Ventilation Institute (HVI).

To eliminate all of the steam from the bathroom after taking a shower, the HVI also recommends at least two or three air changes, or as mentioned earlier, the fan should be left to run for exactly 20 minutes.

Why Should You Leave the Bathroom Fan Running?

The following are some of the main reasons why it’s advisable to leave an exhaust fan running, even after taking a shower:

Steam is Generally Produced Quicker than it’s Utilized.

Many people usually turn on the bathroom fan before showering and then turn it off after taking a bath or shower. But the bathroom fan should be turned on for at least 20 minutes after you’re done. The reason is that steam is generated faster than it can escape from the room.

The problem arises when moisture, due to the steam, starts to build up on surfaces in the bathroom, like tiles. If humidity levels are too high, it can encourage the breeding of mold spores and mildew.

Exhausted Air Once You Run the Fan

Remember that the bathroom is a closed space. With the help of an exhaust fan, you’re exhausting air every time you turn it on. When you leave it off, this air accumulates inside the room and stagnates. This stagnation happens because there is no replacement supply of fresh air to take its place after exhausting out.

Leaving your bathroom fan on ensures that the replacement flow of fresh air replaces the exhausted air. Hence, this can easily prevent the backflow of air or rust in your vent stack.

A continuous flow of fresh air also ensures a decrease in the concentration of moisture or humidity inside your bathroom.

What Happens if Your Bathroom Remains Steamy After Running the Fan for the Recommended Duration?

If this is the case, then there might be a technical issue with your exhaust fan. Some of the most common issues include:

Using a Less Powerful Fan

Using a fan that is not powerful enough may lead to indoor air stagnation when the bathroom is used. This can be very hazardous for your health, especially when you have small children at home.

A more powerful exhaust fan means it’s less likely to fail in its function of exhausting moist air from your bathroom. Your fan should be powerful enough to exhaust at least 50 cubic feet of air per minute (CFM) from the bathroom.

Using a Fan with Incorrect CFM Rating

A fan can’t perform optimally if it has a rating below its minimum CFM requirement. If your required CFM is 50 and you buy a 30-rated fan, you’re compromising your bathroom’s ventilation.

Using a Fan that is Clogged with Dust or Dirt

A fan that has become clogged by dust tends to lose its ability to push air out of your bathroom. This means it will depend on natural buoyancy created by humidity and heat present in your bathroom for its air movement capabilities.

Using an Aged Exhaust Fan

Exhaust fans are mechanical appliances. Like other appliances, they can also become faulty with time and use. A working exhaust fan should be checked for wear and tear at least once every five years.

If you’re experiencing any of these issues, it’s important to check your venting system for air leakage or blockages before installing a new exhaust fan.

Additionally, it’s also essential to clean the filters and grills of your bathroom exhaust fans regularly.


The Fan Might Be Incorrectly Positioned

The fan should be installed and located so that it can easily move air out of the bathroom. If you’re following all the instructions correctly, but your fan isn’t exhausting enough air, then this could mean that there’s a problem with its positioning.

To encourage proper airflow from an exhaust fan, take these steps:

  • Locate the fan at least 6 inches away from any obstruction, like a towel or curtain. Make sure that there’s enough space to allow air movement in the bathroom.
  • Position your fan so that it is halfway between being centered with the bathtub and centered on the ceiling of your bathroom. This means you have to give it at least 2 feet of space from the side walls.
  • Allow one-foot clearance on all sides if you’re planning to install your exhaust fan in a window nook.


Tips for Improving Ineffective Bathroom Exhaust Fans

Because steam will generally dissipate after 20 minutes, you may use these methods to solve bathroom fans that are ineffective temporarily:

  • When you shower, open the windows and doors to allow steam to escape.
  • You can use a dehumidifier on the floor to get rid of the dampness.
  • Put out some moisture-absorbing powders in convenient containers.
  • After showering, make sure you dry the walls.
  • To create airflow, mount a pedestal fan on the wall.
  • Towels should be dried outside your bathroom to prevent them from contributing to the bathroom’s moisture level.


Negative Impacts of Running the Fan Past 20 Minutes

Unfortunately, there are cases where running the exhaust fan for longer than 20 minutes post-showering will cause more problems than it solves.

And here are some of the reasons why this isn’t advisable:

It’s Expensive

Depending on the voltage of your fan and how often it’s used, you can expect to spend up to $113 per year in electricity costs when using a bathroom exhaust fan continuously.

Most homeowners can’t afford such expenses, mainly when limited by their budget and need to use appliances sparingly.

Fans that have been overtaxed usually draw more energy, which means more money goes down the drain. But that’s not all; this will also hurt your fan’s lifespan.

It’s Not Safe

Running the bathroom fan past the recommended duration can also mean putting you and your family at risk. According to the CPSC – the US Consumer Products Safety Commission, fans in the bathroom are dangerous and can start a fire.

This was accompanied by a study they did in 2017, where 75% of the reported fire incidences happened in restrooms and bathrooms. And about 80% of these reported events occurred in residences.

So, how can fans start fires?

Excessive bathroom fan operation leads to thermal wear. As a result, the fan’s thermal cutoffs will eventually fail. When this happens, the temperatures of the fan’s motors can’t be controlled or limited, which may cause them to ignite and start a fire as a result of rising high.

Additionally, lint accumulations and worn-out bearings can cause the motors to overheat, causing them to burst into flames.

What then should you do?

Installing a Timer Would Be a Great First Step

Under certain circumstances, some individuals deliberately switch on the bathroom fan to be sure it works properly. Others, on the other hand, forget to switch it off after use.

Installing a high-quality timer is the ideal option for both expense and energy savings, as well as ensuring that your fan offers you prolonged use.

Make Use of Dual Speed Fans

Dual speed bathroom fans are specifically designed to sustain prolonged use. Yes, you can leave these bad boys on longer than 20 minutes after showering without worrying about them overheating or starting a fire.

You should check the manufacturer’s instructions to ensure the kind of fan you’re using is designed for prolonged use in bathrooms. Also, note that sure fans are only ideal for single speed only – do not engage dual-speed if your fan isn’t made to support this feature.

Wrapping Up

In conclusion, you should leave your bathroom exhaust fan on for exactly 20 minutes after taking a shower. This is because any moisture present in the air must be removed so that mold and mildew do not accumulate.

Leaving the fan on for an additional 20 minutes ensures that all moisture has been cleared from your bathroom, and there will be no mold or mildew growth.

The exhaust fan also removes humidity from the air, which helps prevent fogging of mirrors and other bathroom fixtures.