girl found mold in the corner of your bathroom , in your residential building after renovation

How To Prevent Mold in Bathroom Without Fan

Bathrooms are typically very humid because of the shower, and so mold grows in them very easily. Bathroom fans are great ways of keeping the humidity down, but not all bathrooms have them. So, in this article, I will explain how to prevent mold in a bathroom without a fan.

Overall, keep the humidity below 60% most of the time by opening any windows and the door immediately after the bathroom is used for a shower. If humidity remains over 60%, then use a dehumidifier for 30 minutes a day. Also, wipe down surfaces once a week with an anti-mold cleaner.

It’s virtually impossible to stop mold spores from getting into your bathroom. So, the main ways to stop mold are to make your bathrooms inhospitable to mold by making sure it doesn’t stay damp for extended periods of time and by eliminating mold before it can get started. 

Below, I will provide a rundown of the conditions that mold likes to grow in and step to take to stop it from growing when your bathroom doesn’t have a fan.

How To Stop Moisture in a Bathroom Without a Fan

The main source of moisture in a bathroom is the shower. After a person takes a hot shower, the mirror, walls, and surfaces have a thin layer of moisture on them. Here’s how to stop moisture from accumulating in a bathroom without a fan.

As a general rule, you should open any windows and doors immediately after taking a shower. If possible, keep a window open when the bathroom is being used for a shower. Use a dehumidifier if the humidity in your bathroom stays at over 60%, even after opening the windows and door.

open small glass window in bathroom

The average humidity in most climates is 30% to 60%. But, during rainy weather, such as when it rains for a few days in a row, the humidity can stay as high as 90%. 

The ideal conditions for mold to grow are:

  • 60% humidity or more
  • Temperatures between 77° F (25° C) and 86° F (30° C)

The temperature that mold likes to grow is slightly above normal room temperature, which is 70° F (21° C). Studies have shown that directly after a shower, the humidity in the bathroom is 100%. But, provided there is good airflow, the humidity in the bathroom returns to the humidity in the whole home and outside after 45 minutes to 60 minutes.

Whereas, with a fan, the humidity will equilibrate after about 30 minutes. I explained this in detail in this article about how long a bathroom exhaust fan should run for. A dehumidifier is very effective at reducing the humidity in a room. 

Ensuring the Humidity Is Too Low for Mold To Grow

Thermometer hygrometer measuring the optimum temperature and humidity in a house

But, to know for sure if the humidity in your bathroom is below 60%, you will need to get what is called a hygrometer. These are reasonably cheap, and you can pick one up for about $5 to $10. 

They are small digital device that tells you what the humidity is. And you can see if your bathroom is a hospitable environment for mold. In very humid conditions, such as at certain times of the year, or in humid regions such as Florida, a bathroom will consistently be over 60%, no matter what you do.

When a bathroom is humid, water will accumulate in the walls and any parts of a bathroom that are made of wood. Even if your bathroom is well-ventilated, the moisture can be above 60%. A dehumidifier will suck out all of this excess water if you use one every day for about 30 minutes every day for 2 weeks.

Wiping Down Surfaces With an Anti-Mold Cleaner

Man cleans bathroom with sponge and cleaning products from the mold

According to the United States Federal Emergency Management Agency (FEMA), to reduce the growth of mold, you should clean surfaces with a mixture of water and 10% bleach. They state that you should wipe it onto a surface and then let it sit for 10 minutes before wiping it off or letting it dry.

They say that this works for surfaces where there is no visible mold growth. If mold is visible, you should wipe it all off first and then apply the bleach solution to the surface. According to the University of Florida (source), a bleach and water solution only remains effective for 24 hours.

After that time, the bleach solution no longer disinfects and kills mold growing. The issue is that mold that has taken root and begun to grow can be visible after a minimum of 3 days. 

Therefore, if the humidity and temperature conditions are right for mold growth, you will need to use the bleach and water solution explained above every 3 days or so. However, if conditions aren’t ideal, about once a week is enough to kill mold before it starts.

Another very important point is that according to the University of Florida, for bleach to be effective at killing mold, it needs to remain wet for a minimum of 10 minutes. 

Therefore, if you wipe on some of the bleach and water solution and it dries in under 10 minutes, you should apply more of it, so it stays wet for over 10 minutes. 

As a general rule, it’s fine to leave the bleach on surfaces after 10 minutes is finished to air dry. The main thing is not to leave it anywhere where it will be touched. The reason is it can accidentally be ingested if someone touches a wall and then eats something without washing their hands. Therefore, you should wipe any areas that could be touched with water. But, after 24 hours, the bleach will be completely inert, and there’s no risk of accidental poisoning. 

Will a Dehumidifier Prevent Mold in a Bathroom

Dehumidifier with touch panel, humidity indicator, uv lamp, air ionizer, water container works in bathroom.

Dehumidifiers do a lot to make rooms feel more comfortable. Bathrooms accumulate moisture from the shower, which can make the conditions in a bathroom ideal for mold growth. But, here’s whether a dehumidifier will prevent mold from growing in a bathroom. 

Overall, a dehumidifier will prevent mold in a bathroom. Mold grows best at a humidity of 60% or more and at temperatures between 77° F (25° C) and 86° F (30° C). The humidity in a bathroom can be brought below 60% with the help of a dehumidifier, which will inhibit mold growth.  

Each time a shower is taken, the humidity in a bathroom goes to 100%. Over about 45 minutes, the humidity in a bathroom will balance out and be the same as the humidity outside and in the rest of a house. While the humidity is above this level, a small amount of mold can begin to grow.

Showers are used often a few times each day. Therefore, each day the shower is used, mold can grow a small amount. Over time, the mold will become firmly established.

What Happens if a Bathroom Has No Exhaust Fan

It’s common for bathrooms to have an exhaust fan or no exhaust fan. A shower causes the humidity in a bathroom to get very high, and an exhaust fan helps to reduce the humidity quicker than a window and opening the door. But, here’s what happens if a bathroom has no exhaust fan.

Overall, the humidity will take 15 minutes more to equilibrate with the outside air and the air in a home compared to no exhaust fan. Studies have shown that an exhaust fan equilibrates the humidity in a bathroom in 30 minutes, whereas without an exhaust fan, it takes 45 minutes.

But, this is provided one or more windows are opened in the bathroom and the door is opened. Also, the rest of a home also needs to have open windows to allow good airflow. Unless you have an inbuilt air filtration system in your home, such as an HVAC system.

Exhaust fans are also incredibly cheap to run, so the reduction in humidity is worth it. I explained how much it costs to run an exhaust fan in a bathroom and an in-depth analysis of how fast an exhaust fan reduces the humidity in a bathroom in this article about how long an exhaust fan should run for. 

Why Does Mold Keep Growing in My Bathroom

Mold is a unique type of plant that takes root in the most unusual places in a home. Mold grows both indoors and outdoors if the conditions are right. If mold keeps growing in your bathroom, this is why it happens.

As a general rule, your bathroom is a hospitable environment for mold, which is a humidity over 60%, and a temperature range between 77° F (25° C) and 86° F (30° C). Normal humidity in a bathroom is 30% to 60%. Use a dehumidifier and ensure there is good airflow in your bathroom.

Mold spores typically can’t be seen with the naked eye and are so light they are held suspended in the air. If there is no airflow, they will eventually settle out of the air and land on whatever is below them. 

But, if there is a reasonably strong gust of wind, they can be blown onto a surface and stick there. Especially if the surface is slightly damp. It’s necessary to keep a house well ventilated to make sure the air quality is good. 

Which involves keeping windows and doors open. Therefore, there is no way to stop mold spores from settling in your bathroom. There are many air filtration systems that will remove mold spores from the air. However, they will not catch all mold spores before they settle on a surface. 

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