IGU Seal and Flexible Spacer Displacement Failures, Field and Laboratory Study

Historically, insulating glass units (IGUs) have most often been constructed using rolled metal channels or tubes to create a uniform air space between the lites. The metal spacer has typically been bonded to the glass with an organic edge seal capable of preventing air, water, and vapor from migrating through the seal. To increase the service life of the IGU and avoid seal failures, secondary seals have often been included on the outer face of the spacers creating a dual-seal system. The secondary seal acts as a first line of defense against water and moisture exposure and improves the ability of the seal and spacer to withstand service loads, including stresses due to pressure differentials that may exist between the exterior environment and the hermetically sealed IGU. Competing IGU seal and spacer designs, materials, and technology introduced in the marketplace have resulted in a new category of IGU seals and flexible spacers that do not include metal tubes or channels, and do not always incorporate secondary structural sealant to bond the flexible spacer to the glass. Some of the IGU seal/spacer designs that have been introduced include spacers that rely exclusively on amorphous organic sealant, subject to cold flow displacement, for fixation to the glass. The authors participated in a large-scale field study conducted between 2008 and 2012 of IGU cold flow seal/spacer displacement in the southwest United States. Included in the study were over 1100 residences with over 30,000 IGUs installed between 1999 and 2006. As part of the displacement study, the effect of internal IGU pressures, glass deflection, edge pressure, and surfaces temperature on seal and spacer displacement were evaluated. Displacement failure rates and failure patterns relating to glass edge pressure, temperature, glass weight, and relative negative IGU pressure are presented. Tests were conducted to further study the degree to which internal pressure and temperature influence the onset, rate, and degree of displacement. Laboratory studies confirm the results of the field study that certain IGU flexible spacer and primary seal combinations can fail due to cold flow displacement when exposed to in-service loads.