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Are Powered Attic Ventilators Ever a Good Idea?

CEO Khai Intela
The heated debate surrounding powered attic ventilators continues to capture the attention of homeowners and building science enthusiasts alike. While my previous articles on this topic have garnered significant interest and engagement, I believe it's...

The heated debate surrounding powered attic ventilators continues to capture the attention of homeowners and building science enthusiasts alike. While my previous articles on this topic have garnered significant interest and engagement, I believe it's important to revisit this subject with a fresh perspective. Today, I will explore whether there are any circumstances where a powered attic ventilator might be justified.

The Problems with Powered Attic Ventilators

Before diving into the specifics, let's recap the issues discussed in my previous articles:

  1. Air Circulation: Powered attic ventilators indiscriminately pull air from various sources, including conditioned air from within the house. As a result, they end up cooling the attic at the expense of the air conditioner, which leads to decreased efficiency.

  2. Moisture and Mold: These ventilators have the potential to suck in moist and moldy air from basements or crawlspaces, leading to potential health hazards within the house.

  3. Backdrafting Hazards: There is a risk of backdrafting when utilizing a powered attic ventilator. This can cause incomplete combustion, resulting in the presence of carbon monoxide in the air, which is a severe health hazard.

  4. Addressing the Wrong Problem: Powered attic ventilators attempt to tackle the issue of radiant heating in the attic, when in reality, the primary source of attic heat is the hot roof deck. Therefore, these ventilators do not effectively address the root cause of the problem.

In addition to these problems, powered attic ventilators are also unlikely to provide any significant cost savings on cooling bills.

Addressing Readers' Questions

Although comments are no longer open on my previous articles, readers continue to reach out with their questions and unique situations. Here are a few inquiries I've received, along with my responses:

  1. Steve W., Pennsylvania: Steve's HVAC company suggested installing a powered attic ventilator to protect his air conditioner from excessive heat. While an unconditioned attic is not ideal for HVAC systems, a powered attic ventilator will offer minimal benefits in terms of extending the unit's lifespan. Instead, consider implementing a radiant barrier above the air conditioner to reduce radiant heat.

  2. Carl S., California: Carl wonders if installing a second gable fan on the opposite end of the house can balance the air flow and avoid pulling hot attic air into the living space. While this approach attempts to eliminate the first problem mentioned earlier, there is no guarantee that it will prevent the exchange of hot attic air with the house. Additionally, multiple fans will consume more electricity.

  3. Nate B., Oregon: Nate experiences hotter indoor temperatures in the evening due to heat being dumped into the house from the attic. To address this issue, Nate should consider a whole-house fan that facilitates a "night flush" to bring in cooler outdoor air during the nighttime. This method effectively cools the house without the need for a powered attic ventilator.

  4. Mark K., Florida: Mark notices hot air pouring out of the soffit vents even before the summer season starts. He contemplates installing attic ventilation fans to eliminate this issue. However, it is essential to understand that a hot attic is not inherently problematic. If the heat is entering the living space, it indicates a need for improved air-sealing and insulation. A powered attic ventilator is not the most effective solution for this situation.

  5. Erika M., Florida: Erika seeks advice regarding conflicting recommendations from an insulation professional and an attic fan proponent. While it's true that excessive insulation can restrict air flow in the attic, installing a powered attic ventilator is not the solution. Attics naturally get hot, and passive attic ventilation does not offer significant benefits. Focus on air-sealing and insulating the house and ductwork instead.

The Exception: No Air Conditioning or Natural-Draft Combustion Appliances

To be fair, there is one scenario where powered attic ventilators can be helpful. If a house does not have air conditioning or any natural-draft combustion appliances, such as water heaters, furnaces, or boilers, a powered attic ventilator can assist in keeping the attic cooler. However, in such cases, it would be more practical to utilize a whole-house fan to cool the entire house, rather than solely focusing on the attic's temperature.

In conclusion, while powered attic ventilators serve a limited purpose, their benefits are outweighed by the potential problems they can create. It is crucial to explore alternative solutions, such as whole-house fans, air-sealing, and insulation improvements, to achieve better indoor comfort and energy efficiency.

Allison Bailes, based in Atlanta, Georgia, possesses extensive expertise in building science as a consultant, writer, and speaker. Holding a PhD in physics, Allison is the founder of Energy Vanguard and author of the Energy Vanguard Blog. His commitment to educating others on building science is exemplified through his work and upcoming book on the subject. Connect with Allison on Twitter at @EnergyVanguard.

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