Use of Glass Mat Gypsum Sheathing as a Substrate for Exterior Insulation and Finish Systems (EIFS)

Abstract

ASTM C1177-compliant glass mat gypsum sheathing is a common building material or substrate over which exterior insulation and finish systems (EIFS) are applied. This sheathing product incorporates proven glass mat technology embedded in a gypsum core that has helped support the EIFS industry, design community, and contractors. Its benefits can reinforce the industry as requirements continue to expand for air, water, and insulation barriers. With the adoption of the 2012 International Energy Conservation Code, EIFS is in a unique position to fully comply with the new standard. The use of glass mat gypsum sheathing in EIFS assemblies has become increasingly necessary as the need for dimensional stability in high-performance energy systems increases. With the new American Society of Heating, Refrigerating, and Air-Conditioning Engineers codes that demand continuous insulation outside the building, along with fully adhered weather barriers, this substrate's dimensional stability is more critical than ever. This paper will discuss the historical development of glass mat gypsum sheathing to meet the evolving needs of the industry. It will delineate glass mat gypsum sheathing's distinctive properties and performance aspects—such as resistance to moisture, fire, mold, and dimensional stability—that make it work for today's construction and building code requirements.