Evaluation of Debonding of Lamina from Foam and Repairs to Exterior Insulation and Finish System Facade

摘要

A large building In Denver, Colorado was constructed in 1999 with exterior insulation and finish system (EIFS) cladding. About a year after completion, the lamina started to debond from the foam on the darker-colored EIFS panels. Tests were conducted to determine the cause of the delamination. The influence of solar radiation was studied. Although elevated temperatures were measured in these areas, they were not above the "melting point" of the foam insulation. During the investigation it was discovered that the pattern of the fiberglass mesh appeared to be "embossed" In the foam surface. Microscopic examination confirmed that the surface of the foam had been locally dissolved in the pattern of the mesh. Chemical analysis and exposure tests performed on the fiberglass mesh used in the lamina revealed that plasticizers migrating from the mesh would attack the interface surface of the foam insulation at elevated temperatures that are below the typical melting point of the foam. The elevated surface temperatures of the darker-colored panels appeared to accelerate the effect of the plasticizers. The scope of repairs at the darker-colored EIFS included removal of the original lamina, preparation of the foam, and installation of new lamina. The mesh used in the new lamina was analyzed to ensure that it dld not contain plasticizers capable of dissolving the foam. The lighter-colored EIFS had not exhibited widespread delamination of the lamina. However, the risk of migration of the plasticizers and the potential for future delamination still existed. Mechanical-fastening was used to secure the original lamina to the framing, then a new lamina was applied over the original lamina. This repair concept was dependent on proper bond between the new and original laminas. The bond was tested using techniques similar to those used for measuring adhesion for both new synthetic and cementitious base coat materials.