Attic Ventilation Fans Pros and Cons: Will They Save Electricity?

Many homeowners are constantly looking for home improvements that make life a little easier and save money. Among the first areas to be considered is the attic. If it's stale, hot, musty, or all of the above, the thought typically arises, “I wish I could put a fan up here and improve the ventilation.” Well, guess what? You can.

These devices, called attic ventilation fans (big shocker, huh?), are what we're going to cover in this article. What do they do? Should your home have one? What are the pros and cons of attic ventilation fans? Do they save money or electricity? We'll explain everything you should know when considering one for your home.

What Is an Attic Ventilation Fan?

As their name implies, attic ventilation fans promote air circulation within the home's topmost space. They're installed and positioned to blow the air inside the attic outside and replace it with fresh air from the outside. This air exchange process yields several benefits, particularly reductions in both heat and moisture in the attic.

How Do Attic Ventilation Fans Work?

During the summer, attics can get warmer than the outside temperature. This bubble of heat lingers over your house, where it spreads and radiates downward, heating the rest of the home. Not only is this hot and uncomfortable, but it makes the air conditioner work harder. So reducing the temperature in the attic can make the rest of the house cooler and reduce the air conditioner's workload.

During the cold winter months, attic fans exchange and move air the same way, but for a different purpose. When the cold air from outside meets the warm air from inside that seeps into the attic, moisture can accumulate. This can lead to mold and other problems like ice damming. Circulating the air with an attic fan can help to prevent moisture from accumulating.

Are There Different Types of Attic Ventilation Fans?

The function that attic fans perform is synonymous with their name. So, if you're picturing spinning fan blades moving air from inside the attic to outside through ductwork, vents, or some other controlled opening, you're on the right track. There are a few styles of attic fans, and they have slightly different features, yet they all accomplish the same task - promoting airflow in the attic.

Electric Attic Fans

Electrical fans are the most common and the most efficient. These are usually installed on the roof or gable wall, and they're hardwired into the electrical system. Electric fans are often controlled by a thermostat and turn on when the attic reaches a specified temperature. For example, if the thermostat is set to 90 degrees, the fan turns on when the attic reaches 90 degrees and remains off otherwise.

Solar Fans

Solar fans are similar to electric fans, but instead of plugging into your home's electrical system, they have integrated solar panels and run on solar energy. They're not usually controlled by a thermostat, but rather run continuously as long as the sun shines. This means adequate and unobstructed sunlight is a must in any location you're considering.

Wind-Powered Turbines - aka Whirlybirds

Have you ever seen the metal, rooftop-mounted fans that spin with the wind? These wind-powered turbine fans, affectionately known as whirlybirds, are a favorite for homeowners looking for a passive, low-cost option. As long as the wind is blowing - and it doesn't need to blow hard - they're moving the air without affecting your electric bill. Their passive nature makes them less powerful than electric or solar fans, but they're still remarkably effective.

What Are the Benefits of Attic Fans?

The primary function of attic fans is to promote airflow within the attic, which can help reduce temperature and moisture levels and provide several valuable benefits.

Asphalt Roof Protection

A primary benefit of attic fans is that they help maintain the integrity of asphalt roof shingles to slow deterioration and prevent warping. Many people don't know that a poorly ventilated attic accelerates shingle aging and warps the roof's wood sheathing. They won't make your roof last forever, but attic fans may reduce the wear and tear, improving the years of use you get out of your roof and delaying expensive replacement costs.

A Cooler House

During hot weather, the sun will heat the roof, which will transfer to the attic. Attic fans remove warm air from the attic, and that can help keep the rest of your home cooler, too. Air from a hot attic can seep into your house and make your air conditioner work harder and more often. Not only does that increase your electricity bill, but it can also decrease the lifespan of your units.

Discourages Mold Growth

Without good circulation, moisture can accumulate and result in the spread and growth of mold. This is a risk during both hot and cool times of the year. By moving moist, stagnant air out of the attic, attic fans assist with keeping moisture from building up and, ultimately, help to create conditions less welcoming to mold.

Eliminate Ice Damming

Ice dams can cause serious damage for people in some cold climates. It typically happens to attics with poor ventilation during cold weather. Warm air in the attic causes snow on the roof to melt. As the water drips and flows, it ends up refreezing into ice that blocks eaves and accumulates around roof edges. This can lead to mold, as well as water and structural damage throughout various areas of the roof, joists, drywall, and just about anywhere else.

What Are the Cons of Attic Fans?

Attic fans offer many benefits, but they have their limitations, and those are worth considering when deciding if attic fans are a project that makes sense for you.

May Increase Energy Use

The more an attic fan runs, the better ventilation it provides. But if it's an electric fan, it will use electricity. Typically, the energy needed to run the fan negates any electrical savings from better attic ventilation. So if you're wondering if an electric attic fan will help you save electricity, the answer is probably not - what it saves will be a mostly even trade for what it uses.

However, one solution might be to invest in solar-powered attic fan units. They run whenever the sun is shining and don't affect your monthly electricity bill.

Faulty Installation Leads to Leaks

One of the most common reasons for a poor experience with attic fans is subpar installations that lead to roof leaks and damage. Make sure the work is done by a qualified professional with a long-standing reputation for good work. And make it a point to inspect the fan and any vents and openings at least once a year for needed maintenance.

Carbon Monoxide

If you have appliances that use natural gas or propane, an electric attic fan can potentially lead to carbon monoxide exposure. This happens if the fan creates negative pressure and draws carbon monoxide into the house's interior instead of venting them outside.

You can tell if your house has negative air pressure by slightly opening a window while the attic fan runs. If air comes into the house, it has negative pressure.

Regardless of whether or not your home has negative pressure and even whether or not you have an attic fan, make sure you have a carbon monoxide detector installed on each level of the home as a standard safety practice.

Don't Forget the Makeup Air

Makeup air isn't something many people think about regularly, but it matters when talking about attic fans. Remember how the job of an attic fan is to move air from inside the attic to outside? When the air is moved, air from elsewhere is pulled in to replace it. The availability of that air is the makeup air. An attic needs enough passive ventilation from vents and soffits to provide that air. But if those are sealed, obstructed, or just not there, then the conditioned air from within your house will be pulled into the attic, reducing HVAC efficiency and straining the system.

Do You Need an Attic Fan?

When deciding if you would benefit from an attic fan, consider what problem you're trying to solve and what goals do you want to accomplish.

If saving money on your electric bill is your only goal, then an attic fan probably isn't the best solution. The ROI for the cost and installation may take up to 30 years in some cases. And unless it's a solar or passive device, any energy saved is a wash given the energy the fan consumes.

Consider how your home is constructed and if it lacks adequate ventilation now. Do you have continuous venting along the soffit and a ridge vent? If so, an attic fan might be unnecessary. If not, and your attic gets hot during the summer months or accumulates excessive moisture in the winter, and you want to avoid the problems that can accompany those situations, then an attic fan could the best solution for you.