The Science of Experience



Do I Need a Vapor Retarder?

Posted by Emillie Lee

Mar 11, 2016 11:30:00 AM


A common question among spray foam applicators, builders, and homeowners is whether some sort of barrier needs to be used to prevent vapors from polyurethane spray foam insulation from making their way into buildings' interiors. A recent study conducted at the University of Waterloo sought to answer this question once and for all, and the answer they arrived at is a resounding "no." Vapor retarders are not a necessity for spray foam.

The study examined both closed-cell and open-cell spray foam. Using a combination of field testing, climate chamber measurements and computer modeling, the researchers examined the vapors that were or were not released from applied spray foam with and without the inclusion of vapor retardant barriers. They found that typical framed walls were capable of controlling the minimal vapor diffusion that does occur with spray foam.

Because there is concern whether vapor barriers may be needed in more extreme environments, the researchers also evaluated the necessity of vapor retardants in hot and cold climates. They found that for both open-cell and closed-cell polyurethane spray foam insulation, wood framing alone is sufficient to retard vapors when the exterior temperature is very low and when the indoor humidity and temperature are very high.

It seems that the vapors released from polyurethane spray foam are not substantial enough to work their way through a standard wall and be present in the interior structure in levels that would pose a risk to human health. The results of this study serve to re-confirm that spray foam, once it is cured, is a very safe and sustainable choice for buildings.

NCFI Polyurethanes offers a wide array of foam products, from polyurethane spray foam to flexible foam products. We also offer training and certification programs for spray foam applicators. Visit our website to learn more.

Topics: Air Quality, NCFI