Having good ventilation in an attic has numerous benefits. Proper attic ventilation essential for reducing moisture and preventing excessive heat in the attic.  Attic ventilation when done correctly is both high and low attic vents in the form of ridge and soffit vents.  Sometimes good attic ventilation comes in the form of gable vents that have the right number of square inches of ventilation to allow the attic to vent moisture.

However, in pursuit easy or less expensive attic ventilation fixes, some people choose to install attic fans because a contractor said you don’t have enough ventilation and that would cost a lot of money to properly add the soffit vents or ridge vent and only a few hundred dollars to add an attic fan. When given the choice between spending thousands of dollars on proper ventilation an attic fan seems like a good deal…. In theory, these are excellent tools for circulating air in the attic and keeping the attic temperature low.

In fact, they can be harmful to your energy bill, home comfort and create condensation in your attic which CAN lead to mold in your attic.

What Is Attic Fan/ roof power vent?

These fans are a hole in your roof where air can escape to the outdoors. While it may seem silly to meticulously cover a home with insulation, only to leave a place for air to escape, the attic vent serves a few important purposes. It allows hot air to escape in the summer and can also help reduce the chances of ice damage in the winter by allowing a natural flow of outdoor air to ventilate the attic keeping the attic cold and therefore not melting the snow on your roof.

While a simple vent is sometimes used to allow for the passive flow of air, it’s also possible to add a powered attic fan, commonly called an attic fan.

Attic Fans are mounted to the roof of the home and are connected to a power source/ built in solar panel and should only work during the hottest months of the summer and not at all during the winter. These fans draw air from the attic and send it outdoors.

In theory, the air is then replaced by outdoor air, creating a healthy cycle of airflow. If the outdoor air is cooler, then it stands to reason that the home will be cooler because of this cycle.

The problem is… it is not just evacuating the attic but also the conditioned air in your home to the outside!

Attic fans are really drawing climate-controlled air in your home into the attic.  During summer months it will cause your A/C to run longer and make your home feel draftier as it will increase the speed that conditioned air is leaving and draw in unconditioned air from cracks and gaps in your home.

It is hard to predict where exactly the new air, which is replacing the air forced out by the attic fan, will come from. It’s expected that the air will come through the soffit vents into the attic space, but that’s not always the case. If your roof has a slope, then it should have a ridge vent at the peak of the roof to naturally allow hot air to flow out of the attic.

This is where the problem exists.

In many cases, the air being pulled into the attic and then out the ceiling is air-conditioned air. This means you are spending money (through your utility bill) to cool the air, only to have it expelled by the attic power ventilator.

In some cases, it’s reasonable to believe that an attic power ventilator can increase your utility bill by forcing the A/C to work harder to replace the outgoing air.

Attic Power Fans Energy Consumption

While the specifics will change with each home, the consensus is that attic power fans use more energy than they save.

Sources such as The Billings Gazette, Energy Vanguard, and Home Power all have articles that essentially say the same thing: attic power ventilators are simply not worth the cost and effort.

In fact, the Home Power article states that a “typical 250-watt fan would use 180 kWh per month if run continuously.” The entire home, however, only uses about 950 kWh per month, so the ventilation system can encompass a significant amount of energy consumption.