As retrofitting spray foam insulation in older homes has become more common over the last decade, a frequently asked question in the industry is: “Do gas components in the attic become dangerous after spray foaming?” In this article, we’ll dive into why this concern arises and whether it’s something homeowners should actually worry about.

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Two Major Concerns

1. HVAC components like furnaces need fresh air to function efficiently. The concern is that when you spray foam a roofline, you create an airtight barrier, preventing outside air from entering the attic.

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   • This is a legitimate concern, but we’ll explain how it can be properly addressed so that it no longer becomes an issue.
2. Gas appliances with atmospheric venting (e.g., old-style water heaters or furnaces with metal flue pipes) may struggle to vent properly in a sealed attic, leading to carbon monoxide buildup.
   
   • This, however, is not a legitimate concern, and we’ll elaborate on why in this article.

A Common-Sense Approach

First, let’s use some basic common sense. If either of these concerns were actually causing problems, Superior Attic—along with several other large franchises in the industry—would be all over the news for putting homeowners at serious risk. Additionally, companies would be held accountable for replacing thousands of costly HVAC components. The reality is, when installed properly, spray foam insulation does not create dangerous conditions in attics with gas appliances.

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Addressing the Fresh Air Concern

As mentioned earlier, the concern about HVAC components not receiving fresh air is valid—but only if the spray foam installation is done incorrectly. The first step in any spray foam project is to remove the existing insulation from the attic floor, regardless of its condition. This is done by design because the attic will no longer receive air through the roof. Instead, we want some air to escape from the home into the attic, ensuring there’s enough airflow for HVAC components to function properly.

The misconception that spray foam leads to HVAC failure often stems from poor installation practices. Some companies or homeowners leave the old insulation in place to save money or increase perceived energy efficiency. However, failing to remove the insulation prevents proper airflow and can lead to HVAC issues.

Another solution often suggested is installing a fresh air intake duct leading directly to the furnace. This duct pulls outside air into the system, ensuring proper combustion. While some HVAC professionals recommend this, Superior Attic does not find it necessary. In over 10 years of retrofitting homes, we have never had to install one reactively due to a furnace failing from lack of airflow. However, if an issue ever did arise, we would make it right.

Addressing the Carbon Monoxide Concern

The second concern—carbon monoxide buildup from gas appliances with atmospheric venting in a sealed attic—is even easier to address.

• Modern sealed combustion furnaces and water heaters do not rely on attic air. They pull air from outside and expel exhaust directly, making carbon monoxide buildup a non-issue in a sealed attic.
• This is no different from a sealed crawl space. Many homes already have sealed crawl spaces with combustion appliances, and the same principle applies to attics.
• Carbon monoxide detectors serve as a safety net. Regardless of insulation type, homes with unsealed combustion appliances should have CO detectors in place. The risk of carbon monoxide issues exists even without spray foam, primarily due to potential flue blockages or backdrafts.

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Conclusion

Spray foam insulation in attics with gas appliances is safe when installed correctly. The key is ensuring proper airflow by removing old insulation and understanding the role of modern HVAC equipment. While fresh air intake ducts are sometimes suggested, our experience has shown they are rarely necessary. Additionally, carbon monoxide concerns are a non-issue with sealed combustion appliances and proper safety measures in place. When done right, spray foam insulation improves energy efficiency, enhances home comfort, and poses no risk to gas HVAC components.

Would you like to learn more about how spray foam can benefit your home? Contact Superior Attic today!

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