25 years of proof

Dew points measured installation site with portable frost point device.

This article is presented in its full form here on GlassMagazine.com.

The results are in. A 25-year study of insulating glass units based on long-term analysis of in-the-field building performance indicates that independent, third-party certified insulating glass units tested to the most stringent level of testing perform better than IG units tested to lower levels of testing.

Sponsored by the Insulating Glass Manufacturers Alliance, Ottawa, Ontario, the 25-Year Field Correlation Study was an ambitious project that examined in-service insulating glass units in specific residential and commercial buildings in various locations across the United States and correlated appropriate test measures. It was started in 1980 with reports issued at the 10-year, 15-year and finally, 25-year marks. Although there were extensive management changes in terms of the sponsors of the research, IGMA continued its pledge over the years, with the goal to accumulate results at the quarter-century mark.

IGMA, which was the Sealed Insulating Glass Manufacturers Association when the study was first initiated, now has the quantitative results that prove sealed IG units tested and certified to the most stringent industry standards carry better in-the-field performance than those that are not.

“Finally, the validation is here,” commented IGMA Executive Director Margaret Webb CHRP. “It’s been a long process but rewarding. Now we have the documentation that proves that higher levels of testing and certification in fact result in better performing IG units when tested and certified,” she said.

Webb said third party certification is critical in establishing the integrity of these products. “Certified and tested IG units are an assurance to end users, window and door manufacturers, building code officials, architects and specifiers, and consumers that products have demonstrated quality and performance according to the latest, up to date standards,” she said.

Research from the study paved the way for the development of specified test measures and even launched the move to a new harmonized U.S.-Canada IG certification document, ASTM E 2190 Standard Specification for Insulating Glass Unit Performance & Evaluation.

“The Field Correlation Study is the type of analysis few in the industry have attempted or even completed,” said Ray Wakefield, architectural Sales Manager for Trulite Industries, Mississauga, Canada, and chair the IGMA Technical Services Committee. “No other organizations have compiled in-depth data on IG field units over such an extensive period of time,” he said.

“The results are noteworthy in that the overall failure rates of IG units are low, despite a wide geographic range of surveyed buildings, a wide range of different field units and a wide range of environmental conditions. Considering all the variables, the numbers are quite significantly low over that 25-year period. The relatively low number of failures reaffirms the fact that people who buy units certified to the latest industry test standards have more assurances of getting a good product,” he said.

One visible “seal of approval” is a marking on the window spacer between the glass or etched directly on the glass identifying the manufacturer, plant location, certification program and date of manufacture.

SIGMA and the U.S. Department of Housing and Urban Development co-funded the Field Correlation Study as joint sponsors to determine the correlation of field failures to ASTM E774 Class C, versus Class CB, versus Class CBA with CBA representing the most stringent level of testing.

IGMA, which was formed in October 2000 as a result of the merger between SIGMA and the Insulating Glass Manufacturers Association of Canada, was one of the leaders in merging ASTM E773/774, also known as CBA, with the Canadian General Standards Board 12.8 to successfully complete a new harmonized standard that manufacturers can use as a single-source testing and certification protocol. That standard, ASTM E 2190, is the current industry standard and is used in most certification programs.

Tough subject
 

IG units are unique in the realm of manufactured products and the IGMA 25-Year Field Correlation Study established baseline and ongoing quantitative statistics on long-term performance. IG units are a large product with a hermetic seal and are installed in harsh environments subject to ultraviolet rays, water, extreme temperature changes and even oscillating loads. IG units can also be exposed to organic adhesive materials and are often fixed in place by an unknown framing material. Comparisons can be difficult as these units are commonly installed in different environments and under numerous other conditions (frames, locations and directional orientations).

The Field Correlation Study provides insights into improving the glazing systems utilized, manufacturing techniques as well as overall performance criteria of insulating glass. The study included 140 buildings in 40 cities containing a total of 40,000 certified IG units, of which two-thirds were field-glazed commercial units and one-third were residential windows. Of this total sample, the field failure rates of 2,400 IG units in 140 buildings in 14 cities were studied in detail.

The study also incorporated data from results gathered at the 10-year and 15-year marks so contrasts and comparisons could be made. In 1990 an additional study was undertaken to examine more than 10,000 CBA units in 102 buildings from units made in more than 50 manufacturing plants with a failure rate of approximately 1 percent at 15 years. This part of the study was designed to include some of the newer seal and edge technologies that were added since the original study.

In-depth analysis
 

Although applications were wide ranging, actual performance varied little from hot to cold or wet to dry climates or sea level to mountain exposures. Eighty percent of the buildings had no insulating glass failures after 25 years. Glazing systems that held water at or near the edge sealant had accelerated 60 percent of the failures that did occur in the remaining buildings.

The IGMA Field Correlation Study also included two buildings with poorly designed glazing systems that trapped water at the edge seal and while the certified units performed better in glazing systems that were designed to keep water away from the edge seal. These units failed prematurely to their counterparts held in properly weeped glazing systems. The study found that IG systems with marine and lock strip gaskets demonstrated high failure rates due to poor or the lack of proper weep or barrier-type systems. One specific recommendation was that certified units should be glazed with systems that keep water ingress at a minimum and weep water that gets in the glazing system away from the edge sealant.

Based on the information obtained from the 25-year data, it is estimated that the failure rate of C and CB units is in excess of 20 percent, due to the number of buildings re-glazed and known systems that were not properly performing to keep water away from the insulating glass edge. In addition, the number of C and CB units demonstrating failure in the 25-year study (14 percent) had approximately three to four times the number of failures of the CBA units (3.6 percent). This clearly demonstrates that those units that achieved the CBA or highest level of certification outperformed the units that had only achieved the C or CB level of certification that were observed from the Field Correlation Study of 1980. It has further been demonstrated that certification to class CBA of ASTM E 774 demonstrated a much higher level of field performance than Class C and CB.

The initial 1980 study had certified units to class C, class CB and class CBA tested to the ASTM E 774 standard. Frost points were taken on the first seven years and visual inspections taken at 10 years, 15 years and 25 years. Some buildings were not accessible for inspection, some building owners had replaced the units, and some buildings had security issues that prevented inspection. About 1,700 units were examined at the 25-year mark, and approximately 75 percent of the original population was captured in the final inspection

The ongoing results of this study prior to the release of the 25-year report were provided to the ASTM E06 task group that worked on the harmonization of the ASTM E 773 / E 774 (CBA) and the CGSB 12.8 standards with the recommendation to eliminate the lower levels of testing (i.e. Class C and Class CB). This recommendation was adopted, and the new standards were published in April 2002, (ASTM E 2188, E 2189 and E 2190). The predecessor standard, ASTM E 774 was withdrawn by ASTM in February 2006, and it will no longer be considered part of the documentation for the current standard.

“This study guided IGMA in establishing ASTM E 2190,” said Bill Lingnell, PE and owner of Lingnell Consulting Services, Rockwall, Texas. Lingnell is the IGMA Technical Consultant. “But even more importantly the study tells us that those units that are certified to meet these standards, when followed closely, provide long-term IG performance. The product’s success has good potential for being achieved when standards are met,” he added.

Lingnell said those who do certify their products and meet the criteria of the standards have a “leg up on the competition.”

Best practices
 

IGMA encourages the industry to adhere to best practices, to meet the highest level possible certification and to employ industry standards such as TM-4000-90-(04), IGMA North American Glazing Guidelines for Sealed Insulating Glass Units for Commercial and Residential Use. The importance of managing water in the glazing cavity is a critical factor in the performance and longevity of certified insulating glass units. Water held at or near the edge seal of an insulating glass unit will result in premature failure, cause structural damage to the glazing system and may result in the formation of mold. The formation of mold and its effect on the occupants of a structure continues to be a prime health and safety concern for architects when designing buildings.

The use of recognized, published glazing guidelines, minimum sealant dimensions for insulating glass assembly and maintaining a quality assurance program are also critical factors in achieving product longevity. Insulating glass should be certified to ASTM E 2190 (replacing ASTM E 774) for assurances of long term durability against fogging (seal failure) and glazed in accordance to IGMA standards. The IGMA 25-Year Field Correlation Study brings real-world performance and results to further establish a case for quality, tested and certified insulating glass units.

For additional information on the study contact IGMA at 613/233-1510.