Last Updated: Jul 16, 2021
After an exasperating day at work or school, a long, hot shower is often a preferred method for relaxing and letting go of some of that excess stress. Low-flow showerheads can help cut back on the water and energy used by the occasional steamy shower. However, if your bathroom does not have an exhaust fan or an operable window, those long showers might be leading to long-term problems for your home. In this complete guide, Rise takes an in-depth look at the role and importance of bathroom fans in protecting your indoor air quality and maintaining optimum humidity levels in your home. These relatively inexpensive additions to the bathrooms in your home consume limited amounts of electricity while adding several tangible benefits.
Depending on your climate, up to 20 percent of households might be affected by humidity issues. High humidity levels in homes can lead to several problems, both for homeowner health and the building's structural integrity. According to a recent publication by the Environmental Protection Agency (EPA), the ideal indoor relative humidity (RH) for homes should be kept between 30 and 50 percent. When humidity levels rise above 50 percent, mold and mildew growth will almost assuredly begin to grow throughout your home. While we often associate mold with growing on wood, other types of fungi can grow on paper, carpeting, food, and even your insulation when the moisture conditions are correct. Mold and mildew spores are among the leading causes of respiratory diseases, asthma, and other allergies affecting millions of people across the country. In addition, high humidity levels can create ideal conditions for pests such as cockroaches and dust mites.
Bathroom fans are one of the most critical elements of a healthy and energy-efficient bathroom. Besides removing those unpleasant odors associated with bathrooms, they help remove the excessive moisture and even mold spores that build up in the bathroom after hot showers. Many bathrooms are located in rooms without windows. Though building codes and regulations vary by region, many cities and municipalities around the country require the installation of exhaust fans in windowless bathrooms.
Humidity levels in homes can rise due to several factors. The use of humidifiers, steam radiators, dryers, cooking practices, and hot showers in unventilated bathrooms are the main culprits. A bathroom fan, then, is essential to maintain optimum humidity levels throughout your home, remove excess moisture and mold spores, and protect the indoor air quality inside the walls of your home.
HVI Certification for bathroom fans ensures that the product has undergone rigorous performance testing by a third-party organization. The testing required for HVI Certification provides:
Fans without HVI Certification can inflate their performance ratings and may not always meet building code requirements. HVI Certified bathroom fans are widely available from most major brands, and you can even filter for this attribute when shopping online.
As with almost every appliance and energy fixture in the home, the answer to this question is: "It depends." Just as LED light bulbs use only a fraction of the energy compared to older incandescent bulbs, bathroom fans have a wide range of electricity use. The most energy-efficient models who receive ENERGY STAR certification might use as little as 6 watts, similar to a LED light bulb. On the other hand, standard bathroom fans might use upwards of 60 to 70 watts of electricity. Some of the newer models of bathroom fans can include lighting fixtures, which will increase the overall energy usage of the product.
It is worth mentioning that many bathroom fans often come with automatic timers. These allow the bathroom fan to run for 20-25 minutes after someone has taken a hot shower. This timer reduces the energy waste that can occur when the bathroom fan is accidentally left on for extended periods.
Almost all bathroom fans complete the same function of getting rid of excessive odors, humidity levels, and even mold spores that accumulate in bathrooms' moist environment. However, there are slight differences based on where the fans are mounted, how they expel the moisture and air inside bathrooms, and any extra features they might include. The most common types of bathroom fans available on the market today include:
The best type of bathroom fan for your home will depend on the location of your bathroom, the structure and design of your home, and other particular features. Below, we briefly recommend the optimum type of exhaust fan for different kinds of bathrooms.
This type of fan is best for bathrooms located on the upper stories of a home. The exhaust pipe will move up through the attic and vent to the outside through the roof. For this type of fan, it is vital to make sure that the ductwork is vented to the outside. In addition, assure that it is insulated to avoid condensation buildup that could negatively affect the insulation in your attic.
A wall-mounted exhaust fan is for bathrooms located next to an exterior wall. In this type of installation, the fan is set up on the outside of the outer wall. Wall-mounted exhaust fans offer power ventilation coupled with quiet operation.
An exterior exhaust fan is mounted on the exterior of the home. These are great for reducing noise levels inside the house while regulating moisture to prevent mold and mildew
For homeowners who want to improve the aesthetics of their bathroom, exhaust fans that include lighting fixtures are often less of an eyesore and achieve multiple purposes in one unit.
The energy efficiency of bathroom fans is measured by airflow. The metric for measuring this airflow is in cubic feet per minute per watt (cfm/W). Unfortunately, the minimum standard for ENERGY STAR bathroom fans has an efficacy rating of only 2.8 cfm/W. The most efficient models on the market today, however, can achieve a grade of up to 19 cfm/W. If you are searching for the most energy-efficient bathroom exhaust fan for your home, don't only look for ENERGY STAR certification. Instead, check the label for the efficacy rating and prioritize products that achieve a minimum cubic foot per minute per watt rating of at least 10.
Bathroom fans are rated by their cubic foot per minute (CFM) rating. This doesn't necessarily determine the product's energy efficiency as it doesn't look at per-watt usage. However, it can be helpful to size the best fan for your bathroom properly. Most fans come with a CFM rating anywhere between 50 and 110. Homeowners can adequately size the best bathroom fan for their homes by using the following formula:
“Minimum CFM rating required = Length x Width x Height (of your bathroom) x 0.13”
Bathroom fans, when properly maintained, will last for an average of ten years. Dusting and cleaning around the fan intake will help avoid the accumulation of dust and debris, which will put more stress on the fan's small motor. If your bathroom fan is noisier than usual, it might be a sign that it is wearing down and needing replacement.
Bathroom fans make minor amounts of noise due to the small motors, fans, and blower wheels that help expel the moisture-ridden air. Most new models of bathroom fans will make minimal amounts of noise. However, homeowners who want the most silent fans should opt for exterior exhaust fans mounted on the home's exterior.
The optimum amount of time homeowners should run the bathroom fan after a shower largely depends on the shower's length, the size of the bathroom, and whether or not the bathroom has an operable window. However, the Home Ventilation Institute recommends leaving the bathroom fan running for at least 20 minutes. This time will lower humidity levels and get rid of excessive moisture and condensation levels in the bathroom and in the ductwork that takes the moisture outside the home.
Some bathroom fans that we think are great offer additional features, like variable speeds, humidity sensors, motion sensors, and timers. Both Panasonic's WhisperGreen series and Delta's BreezSignature series offer fans that continuously run, at a low, soundless rate, to provide air changes in the home. Then, when they sense higher humidity or motion, depending on which model you choose, they increase the exhaust rate to remove the damp air quickly.
The accumulation of dust can lead to louder, vibrating noises that are not only annoying to listen to but can reduce the lifespan of your fan. Excess dust can settle on the fan blades or the blower wheel. In the worst-case scenario, this can cause the fan to hit the exhaust housing and produce a loud, banging sound. Regularly cleaning and dusting around the fan intake and the entire housing is the best way to properly maintain your bathroom fan.
Tobias runs an agroecology farm and a natural building collective in the mountains of El Salvador. He specializes in earthen construction methods and uses permaculture design methods to integrate structures into the sustainability of the landscape.