The Florida Department of Business and Professional Regulation partnered with the University of Florida's Engineering School for Sustainability Infrastructure and Environment to determine the “Impact of Spray-Foam Insulation on Durability of Plywood and OSB Roof Decks.” Spray foam was applied directly to the bottom underside of the roof sheathing.

Some known facts of the performance of spray-foam insulated wood decks:

• Premature deterioration of wood roof decks (plywood and OSB) occurs as a consequence of long-term, high moisture load in the wood.
• Spray-foam insulation can create a barrier that reduces the drying rates of wood roof decks, which may result in an unfavorable buildup of moisture in the wood.
• Damage investigations of spray-foam insulation wood roof decks have found instances where deterioration of a wood deck has occurred due to water intrusion.

This study did not go directly into the effects that spray-foam insulation has on asphalt shingles, but measurements in the field study revealed that “asphalt shingle temperatures were 21 degrees warmer than a comparable house that did not have spray-foam insulation.”

Industry Note

The Asphalt Roofing Manufacturers Association (ARMA) does not recommend applying shingles directly over insulated roof decks unless an adequate continuous ventilation space, free of obstruction, is provided between the top of the insulation material and the underside of a nailable deck.

How To Use This Info

Spray foam is not an acceptable application to maintain an Atlas shingle warranty without creating balanced airflow under the deck. Discuss alternatives such as fiberglass insulation and cross-vent insulation boards (ACFoam) with customers. Be proactive and take a stand to ensure everyone involved gets a system that works the way it is supposed to by providing proper airflow under the deck.

For more information, contact an Atlas sales rep.