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Insulating Glass Failures

Find the root cause and solutions in continuing education

Insulating glass is used in over 90 percent of the windows and glazed doors sold across North America, according to the Fenestration and Glazing Industry Alliance’s market study. Though IG fabrication is a well-known process, it is sensitive to variations that can lead to early failure in use. Although rare, such failures can be highly visible and may require window replacement. These failures and the ensuing corrections are potentially detrimental to the reputation of the fabricator.

One of the most obvious indications of failure of an installed IG unit in a window or door is permanent fogging—visual obstruction due to a milky-white film on the interpane surfaces of the glass—caused by hermetic seal failure. Fogging can also be due to:

  • Film deposits left on insufficiently washed glass, such as residue of cleaning solution, adhesive or oils from excessive handling, 
  • The accumulation of the products of chemical interaction between volatiles released from components, such as spacers, sealants, muntin bars or grilles, or desiccant or paints, or 
  • Component incompatibility, such as the use of glazing sealant versus IG sealant. 

Another issue is that seal failure can cause loss of inert gas infill, which degrades thermal performance. The common causes of seal and/or spacer failure are fabrication-related.

These issues include:

  • Cracked glass due to excessive edge pressure or poor edge quality from cutting, 
  • Air pockets in the sealant bead, 
  • Poor corner fill, 
  • Poor spacer/glass alignment, 
  • Desiccant that has been left exposed too long before sealing, 
  • Poor mix of sealant, and 
  • Damaged low-E coating.

To help prevent such problems, it is important that IG fabricators and shop floor team leaders understand what material or fabrication process steps tend to harbor the root causes of degradation. They should also understand proper selection and use of compatible sealants, desiccants, spacers, in-fill gases, glass coatings and other components, as well as the elements of testing, packaging, shipping and glazing of IG units. 

The FGIA Insulating Glass Fabricator Workshop offers a hands-on experience for team members associated with the assembly of IG units and the fenestration products that utilize them. The workshop also provides opportunities for career enhancement as well as improvements in product quality and long-term customer satisfaction. 

IG Fabricators Workshop

Since its launch in 2016, the FGIA Insulating Glass Fabricator Workshop has addressed best practices for the most important aspects of fabricating and testing IG units. Over six years, it has hosted hundreds of skilled practitioners of our industry. 

Through a mix of classroom education along with a primary focus on hands-on demonstrations, the workshop showcases best practices for the typical IG fabrication stages, as well as an opportunity to witness the physical testing per ASTM E2190 that goes into certification of IG units as required by NFRC standards, building codes and the ENERGY STAR program.

The next in-person workshop will be held Nov. 1-3, 2022, at the Intertek Testing facility in Plano, Texas, near Dallas. Among the topics covered are:

  • Glass Cutting and Washing
  • Spacer and IG Fabrication
  • Sealants, Hot Melt Sealant, Sealant Adhesion and Butterfly Test
  • Volatile Fog
  • Gas Filling and Measurement 
  • Frost Point
  • Desiccants and Desiccant Matrix
  • Forensic Investigation of IGU Failures.

For those unable to attend in-person, FGIA also offers a video series option. Developed in 2021, this series offers a condensed version of the workshop in 20- to 30-minute segments. 

Registration for the 2022 in-person workshop is now open. Find out more at Contact for more information. 

FGIA at GlassBuild

Catch up with FGIA at GlassBuild, Oct. 18-20 in Las Vegas. Meet with FGIA staff at the Industry Pavilion in booth #1172 and sit in on FGIA’s three educational sessions on GlassBuild’s Main Stage


Janice Yglesias FGIA

Janice Yglesias

Janice Yglesias is the executive director of FGIA overseeing the full organization. She joined the association in 1999 and can be reached at