The correlation of insulating glass units (IGUs) relating to the actual field performance as compared to laboratory testing was a project undertaken by SIGMA (Sealed Insulating Glass Manufacturers Association) that started in 1980. The study was undertaken to establish the correlation between the various levels of testing as outlined in the ASTM E 774 standard for weathering and high humidity/high temperature testing classifications C, CB, and CBA. The study was intended to obtain data on IGUs having visual obstructions in the airspace or seal failures as determined by frost points or visual inspections for 140 buildings in various climates in the United States and compare the results with the classifications of the ASTM standard. The buildings selected had distribution of the units over the three classifications for the standard. The field inspections were conducted at various intervals of five year periods to obtain the data. This paper will present an overview of the study and show the results of the twenty five year field correlation study completed in 2006. The information in the paper will also include data on various conditions that were observed in glazing systems, sealant types in the study, location of the projects evaluated, and data to demonstrate field failure rates for the classifications of laboratory testing. The paper will also highlight a second study that was conducted on over 14,000 insulating glass units with the CBA classification that was started in 1990 and completed in 2005. In addition, information will be presented that is important to the continued use of IGUs for energy savings and long term durability for the future considerations in North America.

The study was originally sponsored by SIGMA and the Department of Housing and Urban Development (HUD) and was continued to completion by the support of the Insulating Glass Manufacturers Alliance (IGMA).

Presented at Thermal Performance of Exterior Envelopes of Whole Buildings X – December 2007

Units: Dual