We Need to Talk about Spray Foam

19 snips

Feb 21, 2025

Dive into the world of spray foam insulation, where closed-cell and open-cell types take center stage. Discover how closed-cell insulation can transform attics into conditioned spaces, enhancing energy efficiency and preventing moisture issues. Learn about the crucial role of low VOC emissions and high R-values in ensuring a healthy home. Matt shares tips on humidity control and the significance of skilled installation for long-lasting results, along with strategies for enhancing roof durability and leak prevention.

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INSIGHT

Ping Pong Water and Open-Cell Foam

Open-cell spray foam can lead to moisture accumulation in roof sheathing, causing "ping pong water".
This phenomenon can cause rot at the roof ridge, especially in humid climates.

ADVICE

Attic Humidity Control

Control attic humidity with a dehumidifier or controlled air supply.
A simple dehumidifier or a more advanced system like a Santa Fe unit can help.

ADVICE

Conditioned Attics

Avoid placing ductwork in unconditioned attics.
This leads to energy loss, duct leakage, and depressurization, bringing hot, humid air back into the house.

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Matt is solo this week for an in-depth discussion on spray foam insulation, focusing on the differences between closed-cell and open-cell foam and the benefits of creating a conditioned attic space. Traditionally, HVAC systems and ductwork are placed in unconditioned attics in the South, leading to energy loss, duct leakage, and humidity issues. By using spray foam insulation at the roofline, homeowners can effectively seal and condition their attic, improving efficiency and reducing moisture problems.

Matt highlights Owens Corning Ultra-Pure Natural Polymers closed-cell spray foam as his preferred insulation choice, citing its high R-value (~R7 per inch), low VOC emissions, excellent air sealing, and moisture resistance. Unlike open-cell foam, which can allow vapor to pass through, closed-cell acts as a Class II vapor retarder, preventing moisture accumulation at the roof deck. This is crucial in humid climates where improper insulation can lead to condensation issues, a phenomenon known as "ping pong water" that can cause long-term damage to the roof structure.

For humidity control, Matt advises builders to install dehumidifiers or controlled air supply in conditioned attics to maintain proper moisture levels. He also stresses the importance of hiring experienced spray foam contractors, ensuring the correct thickness and installation quality.

Another key topic is roof durability and leak prevention. Matt recommends using full peel-and-stick underlayment beneath metal or tile roofs for long-term water protection. He debunks the myth that spray foam prevents leaks, explaining that small, intermittent leaks can go undetected, leading to hidden rot over time.

Tune in for everything you need to know (and more!) about spray foam insulation.

Thank you to our episode sponsor Aquor Water Systems. Learn more at aquorwatersystems.com.

Find Matt and The Build Show on the web:

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Instagram: @risingerbuild and @thebuildshow
YouTube channel: https://www.youtube.com/@buildshow
Website: https://risingerbuild.com/ and https://buildshownetwork.com/

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