A study on the impact of spray-foam insulation.
A study was completed by the Florida Department of Business and Professional Regulation, and 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.” They included spray foam that was applied directly to the bottom underside of the roof sheathing during.
Here are known facts due to spray-foam insulated wood deck performance:
- Premature deterioration of wood roof decks, which includes plywood and OSB, occurs as a consequence of a high moisture load in the wood.
- Spray-foam insulation can create an obstacle that will reduce the drying rates of wood roof decks. This can 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.
As this study did not go directly into the effects of spray-foam on asphalt shingles, but it was revealed that the shingles temperatures were 21 degrees warmer than a home that did not have spray-foam insulation.
According to the Asphalt Roofing Manufacturers Association, they do not recommend applying shingles directly over insulated roof decks due to this. It is highly suggested that an adequate continuous ventilation space, free of obstruction, is provided between the top of the insulation material and the underside of a nailable deck.