Study Supports Class III Vapor Retarder as Suitable for EIFS, According to Dryvit Systems White Paper

WEST WARWICK, R.I., - A study for architects, specifiers and engineers found that in three diverse climates, Exterior Insulation and Finish Systems (EIFS) with a vapor permeable Class III retarder, kept interior wall cavities warm even in the coldest months, thus preventing the possibility for condensation in the exterior sheathing. Conducted in partnership with the Oak Ridge National Laboratory, the study measured the moisture performance of four EIFS wall configurations: EIFS with either 2" or 4" of EPS insulation board and a 4-mil polyethylene vapor retarder and EIFS with either 2" or 4" of EPS insulation board without the polyethylene vapor retarder. Researchers reached their conclusions after evaluating framed walls clad with EIFS without stud cavity insulation in three diverse climates (Boston, Seattle and Minneapolis).

The study's methodology, approach and observations are outlined in a white paper entitled, "Evaluation of the Moisture Performance of EIFS Walls Without Interior Vapor Barriers" published by Dryvit Systems, Inc. Dryvit introduced EIFS to the United States in 1969, with billions of sq. ft. put in place since. To read the white paper, visit

Researchers discovered that for the assemblies and climates tested, EIFS' monolithic exterior insulation properties eliminated the need for a polyethylene vapor retarder to prevent water condensation in a wall cavity. For the three climates investigated, results of the hygrothermal analysis indicate that use of a vapor permeable (IBC and IRC Class III) retarder on the outside face of the exterior sheathing outperforms the use of polyethylene (IBC and IRC Class I) retarder for diffusion control.

"The results show that the EIFS walls with the Class III vapor retarder and without the 4-mil polyethylene vapor retarder dried faster and maintain balanced conditions throughout the year," said Bill Preston, Dryvit's senior engineer/code specialist. "It is also clear that a vapor retarder is not required to prevent water condensation in the wall cavity for the assemblies and climates tested."

Dryvit has led the EIFS industry for over four decades because of its commitment to research and development, and a constant stream of new, high-quality products. That spirit of innovation, coupled with a rigid adherence to ISO Standards for manufacturing quality and consistency, has made the Dryvit brand (Outsulation®) the unquestioned leader in the EIFS industry.

To receive more information about the company or its products, please visit or contact Dryvit at 800-556-7752 ext. 9 or at Connect with Dryvit on Facebook at!/pages/Dryvit-Systems/113389419369. Follow Dryvit on Twitter at!/DryvitSystems.

About Dryvit Systems, Inc.

Dryvit Systems, Inc. ( is the manufacturer of Outsulation®, the premier Exterior Insulation and Finish System (EIFS), in the US, Dryvit operates all North American manufacturing facilities to both ISO 9001:2008 and 14001:2004 standards. Dryvit is a member of and is actively engaged in many relevant construction related organizations such as AWCI, EIMA, NAHB, USGBC, ABAA, AIA, and CSI, and works both independently and within those organizations to promote energy efficient construction methods that create jobs, reduce reliance on non renewable energy sources, and reduce the carbon footprint of our nation's buildings.

A subsidiary of the more than $3 billion industrial sealants and coatings brand holder RPM International, Inc., a Fortune 1,000 Company, of Medina, Ohio (NYSE:RPM), Dryvit is headquartered in West Warwick, Rhode Island and has manufacturing facilities in Georgia, Oklahoma, California, Canada, Poland and China.

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