Can A Whole House Fan Cause Mold? (Find Out Now!)

Ryan Womeldorf
by Ryan Womeldorf

Keeping your home cool provides improved comfort but it can also lead to an increase in electric bills each month. That can facilitate the need for homeowners to implement additional measures of cooling a home. Whole house fans are a common way of doing this, but some people worry that a whole house fan causes mold.

There’s no direct evidence that a whole-house fan causes mold, but there’s a correlation between them and homes with mold in the attic. The hot air that the fan distributes out of the house can lead to extra moisture trapped in the attic. Therefore, a yearly inspection is a good idea to check for any contributing factors to mold growth.

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Are Whole House Fans Responsible for Mold?

While there is no direct evidence that whole-house fans are responsible for mold, there is a common link between homes with whole-house fans and mold appearing in attics and vents.

The hot air that is taken in by the fan and distributed out of the house can lead to additional moisture from the humid air. This humid air can become trapped in the attic, leading to mold growth.

Having a whole house fan doesn’t automatically mean that mold will grow in the attic, however. Having a yearly inspection is a good way to catch any factors that can contribute to mold growth as well as detect any mold that may already be on the property.

How do Whole House Fans Work?

The idea behind a whole house fan is that it creates negative pressure. The fan works by pulling air in through open windows. The fresh air, cool air then enters your home. When the negative pressure begins building throughout the house, it eventually creates a positive pressure in your attic.

When the pressure in your attic builds, it then releases by pushing that air out through the soffits in the eaves of the home or through any ventilation that may be previously installed in the attic space. The intended effect is of a cool breeze and the rooms that have open windows will get the greatest overall impact.

The idea here is to create a strong draft throughout the home, mitigating the need for costly cooling systems to run on a regular basis.

Whole House Fan Installation

Although whole house fans may be more complicated to install than a conventional attic fan, either option should be handled by a professional. The project requires the skills of an electrician, a carpenter, a sheetrock specialist, and a finisher. Without a sheetrock specialist and finisher, you put the appearance of your home’s interior at risk.

Opting for a professional install will also ensure that everything is installed correctly, proper ventilation is achieved, and all building code requirements are met.

Costs to Install

The installation costs for a whole house fan can range as low as $700 to as high as $2,750. The national average is in the $1,250 to $1,830 range for homeowners. This all depends on what unit you purchase and who you go with for the installation.

Installation TypeCost
Attic Fan$200-$1,300
Whole House Fan$700-$2,750
Whole House Fan Average$1,250-$1,830
Whole House Fan High-End$2,000-$2,750

Despite the relatively high initial cost, it can result in substantially lower energy bills over its life span. While it may be tempting to opt for the cheapest available option, investing in a quality whole house fan can really make for an attractive addition to a current home.

What are the Positives of a Whole House Fan?

During the summer, the last thing that anyone wants is to be uncomfortable in their own home. Air conditioning is quite effective at cooling down a space of any size, but they can also be quite costly. When summer temperatures begin to spike, so too can cooling bills. This is what facilitates the need for alternative cooling methods.

Whole house fans work to quickly cool the home off by essentially creating a draft in the home. The fan pulls in the cool air and pushes out the hot air, creating a cooling effect without the need for constantly running costly air conditioning. This leads to improved energy efficiency since whole-house fans use less energy than an air conditioning system. In fact, running a whole house fan can cost you 90 percent less than running your central air conditioning unit for a similar amount of time.

What makes a whole house fan environmentally friendly is that it doesn’t use any refrigerants. While there has been a transition in recent years to friendlier coolants, some of the older versions can be damaging to the ozone.

Whole house fans are also built for durability. If it is installed properly, it should be able to run quietly and efficiently for years to come. Even better, the constant flow of air can not only help to cool a home but can fight against odors caused by pets, cooking, smoking, and household cleaners for a fresher overall smell.

What are the Downsides to using a Whole House Fan?

Implementing a whole house fan can be a great way to save on energy costs, but there are caveats to be aware of. The first is that they won’t work particularly well in areas of high humidity.

Humidity is when moisture gets trapped in the air; by distributing air throughout the house, there is a chance that the moisture can become trapped. When moisture is trapped in your home, it can lead to the growth of mold and mildew.

Cost is another downside. Attic fans run maybe a few hundred dollars whereas a whole house fan can run upwards of a thousand to have installed. Worse yet, it can’t be used in the winter because of the potential for heat loss, requiring your heating system to work overtime.

What’s the Difference Between a Whole House Fan and an Attic Fan?

Whole house fans share quite a few similarities with an attic fan. Both are meant to cool down the spaces that they inhabit, though an attic fan is limited to the attic space. The goal of both is to make it easier to keep the rest of the house cool and use less energy.

An attic fan may be able to help cool the rest of the house but will likely have a limited impact in doing so. A whole house fan, as it suggests, cools down the entirety of the house through the circulation of fresh air. This can make it a more effective option over attic fans, though the latter is certainly more cost-effective.

Additionally, due to the substantial amount of negative reviews on attic fans in recent years, having one will not increase your home’s resale value. While it won’t hurt your home’s value or make it hard to sell, whole house fans, on the other hand, can actually increase the resale value of a home.

So long as you live in the right climate, a whole house fans are often seen as a green alternative to central air conditioning. As a result, homes with whole house fans are often very desirable to prospective buyers.

When to Use a Whole House Fan

Unlike air conditioning, which you can use any time day or night, this isn’t the case with a whole house fan. There are specific times where using a whole house fan will be the most effective.

Try to keep the fan on during the evening hours. This is when the temperatures have started to cool down. You want the air that circulates throughout your home to be dry and cool to prevent humidity from building up throughout your home. Trapped moisture is the leading cause of mold in homes.

Whole house fans tend to be most effective in the cooler temperatures of the early morning and evening. The ideal outside temperature for these units is at least five degrees Fahrenheit below the intended indoor temperature. When the temperature rises during the day and becomes higher than that of the outdoor temperature, keep the fan off. There can come a point where the air outside is simply too hot and the whole house fan simply pushes it around your home.

For best results with a whole house fan, you should not use it alongside a central air conditioning unit on a daily basis. Circulating the humid outdoor air through the central unit all day creates an unnecessary amount of stress on the air conditioning system. However, this does not mean that your home cannot have both a whole house fan and a central air conditioning system. You should just use them at different times.

Stick to your central air unit in the summertime when nighttime temperatures sit above 80 degrees. Whereas, a whole house fan is the better option for the cool evening temperatures of fall and spring.

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Whole House Fan Noise Levels

Depending on the model that you choose, whole-house fans can be quite loud. If the unit has been improperly installed, the problem can worsen. Generally speaking, a large-capacity fan that runs at a low speed should make less noise than if you went with a small fan that was operating at a much higher speed.

When installed, whole-house fans often come with felt or rubber gaskets. This is meant to dampen the noise created by the fan. The age of your fan can come into play as well. If the fan is older and has substantial wear and tear, it can be louder than some other newer units and could indicate needing to replace the old unit.

Ryan Womeldorf
Ryan Womeldorf

Ryan Womeldorf has more than a decade of experience writing. He loves to blog about construction, plumbing, and other home topics. Ryan also loves hockey and a lifelong Buffalo sports fan.

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