The Fenestration and Glazing Industry Alliance has released an updated advisory guideline aimed at helping the industry better identify and assess visual obstructions within the cavity spaces of insulating glass units (IGUs).

The document, IGMA TM-3100-26, Voluntary Guidelines for the Identification of Visual Obstructions in the Cavity Space of Insulating Glass Units, is intended for a wide range of stakeholders, including designers, specifiers, fabricators, installers and end-users across commercial and residential applications. It replaces the previous version issued in 2009, reflecting updated industry experience and expectations.

Within the guideline, visual obstructions are defined as any materials or elements located inside an IGU that unintentionally and materially interfere with a person’s view through the glazed opening. The guidance draws on the collective expertise of IGU manufacturers, glazing material suppliers, engineers and consultants, offering a consistent framework for identifying and evaluating such issues.

While the document is not a mandatory specification, it is designed to support informed decision-making when assessing whether a visual obstruction falls within acceptable limits. By providing clearer definitions and evaluation criteria, the guideline aims to reduce ambiguity and promote consistency across projects.

According to Dave Cooper, Vice Chair of the FGIA Visual Quality Guidelines Task Group, the IGMA TM-3100 series has long been a trusted reference within the industry. He noted that the updated version continues to define what is considered acceptable under recognised industry criteria.

IGMA TM-3100-26 is now available for purchase through the FGIA online store, priced at $80 for members and $230 for non-members.