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Does My Roof Need to Breathe?

attic insulation | FAQ

Does My Roof Need to Breathe? Blog Feature
Amanda Ringler

By: Amanda Ringler on March 20th, 2024

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While researching insulating an attic with spray foam insulation, you may have seen that it is essential for the roof of your home to breathe.

Well, that’s not necessarily correct.

RetroFoam of Michigan has more than 20 years of experience insulating thousands of attics across the Lower Peninsula. With that experience comes the knowledge of how to insulate an attic in a way that keeps your home comfortable and running more energy efficient while saving you money.

Here's everything you need to know about spray foam attic insulation and how it affects your roof. 

Insulating an Attic Roof or Floor with Spray Foam

When it comes to insulating an attic, you essentially have two main options -- applying spray foam to the attic roof deck or the attic flat or floor.

Applying spray foam insulation to the attic roof incorporates this area into your home's conditioned space. This means that the air from your living areas will ascend to the attic, encounter the spray foam air barrier, and then recirculate back into the living spaces, maintaining a more consistent indoor temperature.

Alternatively, insulating the attic flat with spray foam creates a distinct separation from the rest of your home. This method effectively prevents the air you heat or cool from escaping through the attic, ensuring your HVAC system works more efficiently and your home remains more comfortable.

The choice between these installation methods also influences the functionality of your attic venting systems. It's important to select the option that best aligns with your home's design and your energy efficiency goals.

Unvented Attic System

When opting for an unvented attic system, your insulation contractor applies spray foam directly onto the house's roof deck.

There's a common worry that this approach might lead to what's known as a "hot roof" or impede the roof's ability to "breathe." However, the notion that a roof requires ventilation to breathe is a bit of a misconception.

Originally, attic ventilation served primarily to expel moisture, which infiltrates the attic space through small openings in the roof deck. By applying spray foam insulation across the entire roof deck, these gaps are sealed, preventing moisture entry. Consequently, this sealing eliminates the need for attic ventilation to remove moisture since the air barrier formed by the spray foam already keeps it out.

Concerns about the creation of a hot roof are largely unfounded. This term is a relic from the early days of attic insulation, based on the incorrect belief that insulation acts as a heat source. 

Now, let's shift our focus to understanding the structure and function of a vented attic system.

Vented Attic System

In some rare cases, it makes more sense and is more beneficial to insulate the floor of the attic instead of the roof deck.

This is considered a vented system.

The first thing a good contractor must keep in mind is circulation. When you insulate the floor of the attic with spray foam, you are cutting that space off from the rest of the house, creating an air seal. When this is done the attic must be vented.

The purpose of the vents is to bring cool air from outside into the attic to help it maintain a constant temperature, according to Energy Star.

The problem with this system is that the temperature difference between the attic and the rest of the home causes condensation, which promotes mold and mildew growth.

Learning More About the Benefits of Spray Foam Insulation

Now that we've cleared up that your roof doesn't actually need to breathe, you might be yearning to learn more about spray foam insulation for other areas of your home.

If that's the case, check out our foam insulation Learning Center. You'll find a ton of great resources there, as well as answers to the most frequently asked questions.

Related Articles

Clearing Up Misconceptions About Spray Foam Insulation

Does Spray Foam Damage Roof Shingles?

Vented vs. Unvented Attic: Which is Better?

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About Amanda Ringler

Amanda previously has worked as a breaking news and crime reporter, TV news producer, and editor in Flint and Detroit. Throughout her career as a journalist, she has won several awards from The Society of Professional Journalists - Detroit Chapter and the Michigan Press Association. As part of the RetroFoam of Michigan family, Amanda uses her experience as a journalist to write content that will help educate homeowners on the benefits of foam insulation. When Amanda isn’t writing, she’s spending time with her husband and rescued huskies. She also loves knitting, making art, cooking, and hosting dinner and a movie night for friends and family.