Polyisobutylene, or PIB, is a synthetic rubber commonly used as an edge sealant in Insulating Glass Units (IGU’s).  IGU’s consist of multiple glass panes within a window frame (e.g. “double-glazed” and/or “triple-glazed” windows), and serve the purpose of insulating building interiors from both sound and thermal transmission. These IGU’s are typically separated by “spacer bars” and sealed at the outer edges of the panes to the spacer bars between those panes. PIB is the most commonly used primary sealant for this purpose. There are multiple manufacturers of PIB, just as there are many manufacturers of windows/IGU’s which incorporate the PIB edge-sealant into their finished products.

Over the past year or more, we are seeing an increased incidence of “PIB movement” claims arising in construction defect cases. Owners, developers, general contractors, and the window manufacturers themselves, are filing claims in increasing numbers against the manufacturers of PIB products based upon the products migrating from their appropriate placement at the edge of the windows, into and obscuring the IGU’s fields of vision. This is particularly true in the cases of multi-unit, multi-story HOA complexes, where double and triple-glazed windows are becoming commonplace.

As these claims continue to grow in number, further investigations are being performed to determine if the migrating PIB is in fact due to a product defect, if the PIB is being improperly installed, and/or if its use is contraindicated in high-heat environments. The jury is still out on the answer to these questions, but for now, building professionals of all ilks would be well advised to take a hard look at the causes of this growing PIB issue prior to installing PIB-edge-sealed windows into their respective upcoming projects.