Are power attic ventilators smart to use?

Attics can get hot. At a certain point — if this heat starts to affect comfort, for example — homeowners may decide to take action. Maybe the attic surrounds the living space of a home, and the heat is being felt inside; maybe certain rooms just aren’t comfortable in the summer; or maybe that bonus room above the garage is feeling toasty and never cools off.

One technology designed to try to manage this issue is the power attic ventilator, a type of fan that is typically installed on either the gable end or roof deck of an attic. Its goal is to cool off the space by exhausting the hot air inside and replacing it with cooler air from the outside. But how does it work?

Source: Steve Rainwater (

The short answer is “not well,” and ideally this approach would not be used at all. Let’s look at some of its downsides before turning to more effective solutions.

Although power attic ventilators can provide relief in the summer, how they go about doing that is often not ideal or cost-effective. For one, they can steal air from the conditioned space of the home, forcing air conditioning units to work harder, use more energy and, therefore, raise utility bills. But that’s not all. Some units are so powerful that they may cause other appliances, such as gas water heaters, to backdraft, putting carbon monoxide into your home.

Behind these concerns is the broader point that the fans may not actually address the root of the problem, just its symptoms.

Fortunately, there are alternative approaches that better treat the issues at hand. One is to confirm that your home’s existing ventilation components — its soffit vents, ridge vents, etc. — are functioning correctly. Building codes require particular rates of ventilation, but home upgrades, such as new exterior paint or aesthetic changes, could unintentionally hamper vent performance.

At the same time, make sure your building envelope (the physical separator between the conditioned and unconditioned spaces of the home) is optimized. From fire, health and energy perspectives, there should be no holes between the conditioned and unconditioned spaces, so any that you notice along the walls, ceiling (whether flat, sloped or vaulted) and floors should be air sealed. In addition, maintain an appropriate amount of insulation and ensure it has been installed correctly.

While a power attic ventilator might seem like a simple, quick fix to help keep your attic and living space cooler, it may do more harm than good. Instead, adding air sealing to your home so that the conditioned air stays inside and the unconditioned air stays outside can do wonders to maximize your comfort without increasing your utility bill each month.