Skip to main content

Insulating Glass

IG certification testing and application workshops help ensure long-term energy savings

IG certification is offered through three programs supported by the Fenestration and Glazing Industry Alliance: 

  • ALI/AAMA Sealed Insulating Glass Certification Program operated by Associated Laboratories Inc.
  • IGCC/IGMA Insulating Glass Certification Program 
  • IGMAC Certification Program

Insulating glass has become the standard for window units intended for all but the southernmost parts of Florida, Texas and other regions in the Southwest U.S., Double glazing is reaching near-saturation market penetration in the U.S. of 97 percent of residential applications, according to the AAMA U.S. Industry Statistical Review and Forecast. 

One of the important factors in the overall long-term thermal performance of a complete fenestration system is the performance and durability of its insulating glass. In addition to the glass panels and edge spacer, an IG unit consists of a rather complex combination of desiccants, sealants, gas fill, glass coatings (low-emissivity, reflective, etc.) and (optionally) muntins or grids. All of these must work together to prevent failure.

Despite this complexity, IG has an excellent track record for durability. Yet, failures can occur. Compromised spacer seals are one of the most common failure modes, which allow moisture to penetrate the space between the panes of glass and condense onto the glass surfaces to cause fogging or frost. Also, any original inert gas fill (typically argon) can slowly leak out, lessening the thermal insulating performance. In addition, the oils, solvents and plastic in the spacers, sealant, desiccant, solvents, and any muntins or grids can release a volatile “chemical fog” that can deposit on the glass surfaces within the IG unit. Certain low-E coatings can oxidize as a result.


The ability of an IG unit to resist such failure is spelled out by recognized consensus specifications in the U.S. and Canada. The foundational specification is either ASTM E2190-19, Standard Specification for Insulating Glass Unit Performance and Evaluation (originally released in 2002), or the National Standard of Canada CAN/CGSB-12.8-2017, Insulating Glass Units. Both outline performance requirements indicative of durability for IG units with one or two airspaces (double or triple glazing). 

To meet the North American Fenestration Standard, windows must be constructed with IG units that meet ASTM E2190 or CAN/CGSB-12.8, which is also required for third-party thermal performance certification by the National Fenestration Rating Council and, by extension, for inclusion in the Energy Star program. 

ASTM E2190 references several essential test methods that use UV radiation and elevated temperatures to impose accelerated simulated weathering conditions in the laboratory to assess IG performance and establish third-party certification. The standard requires that the units:

  • Pass a dew point test, 
  • Resist high humidity and weather cycling, 
  • Do not have internal components that release chemical substances that could potentially affect the integrity of the unit, and 
  • Retain a minimum quantity of inert gas after being cycled through real-world condition simulations. 

The CAN/CGSB 12.8 standard has a similar testing protocol of initial dew point, volatile fog, humidity and weather cycling, and argon gas content, but with variations in some of the prescribed requirements and procedures.

Additionally, to help with understanding how IG units pass such rigorous testing, earn certification and maintain performance over many years of service, FGIA (formerly AAMA and IGMA) offers the IG Fabricator Workshop, typically in November. 

Since its launch in 2016, more than 300 industry professionals have experienced classroom sessions and hands-on laboratory demonstrations to discover best-practice fabrication “dos and don’ts” for cleaning, cutting and handling glass, and selecting and applying desiccants, sealants, gas fill and more. The highly popular forensic investigation segment of the workshop was offered in repeated sessions during the 2019 GlassBuild America show and is being expanded for future workshops. For more on upcoming workshops, visit 


Janice Yglesias

Janice Yglesias

Janice Yglesias serves as the executive vice president of the American Architectural Manufacturers Association, overseeing all daily operations. She joined the association in 1999. She can be reached at