Is An Attic Fan Necessary (Even With Ridge Vents)?

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Attic ventilation may not be the first topic that comes to mind when you think about home maintenance, but it’s essential for several reasons. Proper ventilation ensures your roof’s longevity and prevents heat/moisture buildup in the attic, excessive energy consumption, and ice dam formation along your roof’s edge. Given its importance, some homeowners might wonder whether an attic fan is a worthwhile supplement to their ventilation.

An attic fan isn’t recommended if you have ridge vents. In this scenario, the attic fan will draw cool, conditioned air out of your house and raise your A/C bill. It could also stop hot air from exiting through the ridge vent and pull in rainwater during a storm, which can eventually make your attic leaky or moldy.

We know that’s a lot to take in, which is why we’ll discuss attic fans in detail in this post! We’ll tell you when having an attic fan can improve your ventilation and when you should run it.

An attic of a house with visible wood membranes and an attic fan, Is An Attic Fan Necessary (Even With Ridge Vents)?

Do I Need an Attic Fan?

An attic fan may seem like a great way to keep your attic cool, but it’s rarely the best answer. Let’s take a look at how proper airflow in an attic works so you can see what we mean.

Normally, cooler outside air enters the attic through the soffit vents, which are located under the roof’s eaves, and hotter air exits the attic through gable or ridge vents located on the exterior wall and the roof’s peak, respectively. Please note that gable vents are unnecessary if you already have sufficient soffit and ridge vents. Under these circumstances, they can even prove detrimental to proper airflow in your attic.

This process is essential for several reasons, one being that it stops your attic from getting too hot and eventually passing that heat into the house’s living areas. This extra heat makes your air conditioner work harder, thereby increasing your cooling bill.

Attic fans are intended to help move hot air out of the attic, but they don’t make much of a difference unless your attic doesn’t have enough ridge and soffit vents (you should have an equal amount of both types of vents). Otherwise, the fan could pull in air from outside the house as much as it expels hot air from the attic. You also risk forcing cool air out through the ridge vents, which increases your house’s temperature and puts more strain on the air conditioner.

In summary, it’s possible to get some worthwhile use out of an attic fan, but you’re better off just installing the right amount of soffit and ridge vents in your roof. You should only get an attic fan if this isn’t possible for your house.

For more information on soffit vents and how they fit in with other areas of attic insulation, check out our post on them.

What Should An Attic Vent Fan Be Set At?

There’s no single temperature that’s universally accepted as the best setting for an attic fan since the ideal one for your needs depends on your area’s general climate. If you live in a warmer climate like Arizona, you should set your fan to a higher temperature than someone living in a colder climate like Minnesota, or it’ll run endlessly, and your electric bill will skyrocket.

Generally, though, you don’t want your attic to get more than 10-15 degrees warmer than the temperature outside, and for most homeowners, that means keeping their attic between 90 and 110 degrees Fahrenheit. However, there is an exception to this rule, which applies during the winter, which we’ll discuss in the next section.

Should An Attic Fan Run All The Time?

Your attic fan shouldn’t run all the time. If you think your fan is running too often, it might be set to the wrong temperature (see our previous section), or perhaps it needs maintenance or replacing.

During the summer, you should run the fan during the day since the sun is warming the roof and, consequently, the attic. If the weather is particularly hot, you may want to keep the fan running for a while after sunset as well so you can be sure the heat is dispersed.

You should still run the fan during the winter since the hot air from your house’s interior will pass through the attic. That warm air carries moisture, which can accumulate over time unless the fan helps it evaporate.

Additionally, a warm attic will heat the roof and melt any snow on top. The water then runs down to the eaves and freezes, which creates an ice dam that blocks more water and makes it back up under the shingles. This process can damage the roof, the attic’s insulation, and the house’s walls. To avoid this occurrence, set the attic fan thermostat to below freezing during the winter.

Is It OK To Run An Attic Fan All Night?

Yes, you can run an attic fan all night, but you should only do so when it’s colder outside than it is in your home. As always, make sure that the fan only runs when you want it to, and call a professional if you think the fan tends to turn on when it shouldn’t and might be defective.

Can You Run An Attic Fan With The AC On?

We’ve already discussed this in another post, but we’ll give you a quick recap here.

You can run the attic fan and your AC simultaneously. In fact, the fan can help your air conditioner since, as we mentioned earlier, cooling the attic prevents hot air from entering the house’s living areas. On the off chance that your AC breaks down in the middle of summer, your attic fan can help keep the house cool while you get repairs or a replacement.

Keep in mind that you’ll rack up some hefty cooling bills if you make a habit of using your attic fan and AC simultaneously. Your fan is also more likely to need maintenance sooner if you use it more often. All in all, your attic fan can work as a supplement to your AC unit; just make sure you don’t overuse it.

Final Thoughts

Attic fans aren’t always necessary, but they can still help your home’s air circulation and reduce the chance you’ll have to deal with a damaged roof system, wet/moldy insulation, or high energy bills. Now you can determine whether or not you need an attic fan and, if so, how to use it effectively.

Thanks for reading, and for more great HVAC know-how, stick with us here at HVACSeer.com!

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