History Holds Evolution

Margaret Webb, IGMA executive director, takes the effort quite seriously, almost personally. On the job, visiting members, attending meetings, she is quick to examine any and all windows during her travels, searching relentlessly for that stamp on the spacer bar indicating the IGU has met the certification program requirements. That "seal of approval" is an etched marking on the window spacers between the glass or a label on the glass itself and identifies the IGU manufacturer, plant location, certification program and date of manufacture.

"Without proper third-party certification, there's a chance IG units will fail, and that leaves a bad taste in the mouth of the industry and the end-user," Webb says. "The mechanism for scientific testing and procedures has now been carefully established and documented by a consensus of industry members and third-parties and much time and effort has been spent by IGMA and other organizations to bring this document to market. There's not a single reason to not test to this new standard−it brings a higher level of understanding, credibility and performance to the manufacturing process in the creation of IG units in the U.S. and Canada.

"Why should the architect care? Because it's up to them to bring to their end-user the best performing products on the markets, ones tested to certified standards in real-world performance applications and with the longevity of the individual unit first and foremost," she said. "No one", she adds, "wants to see insulating glass units that fail, leak or worse yet, look like an eyesore in an otherwise reputable building façade."

Field Correlation Study Provides Backbone

In 1980, SIGMA and HUD (Housing and Urban Development) funded a 25-year field study to determine the correlation of field failures to ASTM E 774 Class C, vs. Class CB, vs. Class CBA with the CBA class representing the most stringent level of testing. ASTM E 773 and E 774 were predecessor standards to the new harmonized standards identified as ASTM E 2188, E 2189 and E 2190. This study was completed in December 2005 with the final report covering the 25 year period published by December 2006. (Final reports Preliminary data results on the study were due out presented in February 2006.)

The study included 140 buildings in 40 cities containing a total of 40,000 certified IG units of which 2/3 were field-glazed commercial units and 1/3 were residential window units. Of this total sample, the field failure rates of 2,400 IG units in 140 buildings in 14 cities were actually studied.

Performance varied little from hot to cold climates, wet to dry climates or sea level to mountain exposures. Eighty percent of the buildings had no failures at all and glazing systems that held water at or near the edge sealant had accelerated sixty percent of the failures that did occur in the remaining buildings.

The 25-Year Field Correlation Study actually encompasses two separate studies. The original study, co-funded by SIGMA and HUD, was started in 1980 and included sampling from 140 buildings in 40 cities containing 40,000 certified insulating glass units with representative constructions. Locations of the units were supplied by 28 manufacturers with multiple plant locations. 2,400 units were selected of which 2,100 were accessible at 10 years; 1,952 at 15 years and 1,714 at the 25 year mark.

The second study started in 1990 included newer technologies and a larger sample size of which over 10,000 units were accessible at the 15 year mark. The second study only looked at CBA units from 102 buildings representing 52 manufacturing plants.

Of interest to the industry is that the failure rate observed from the 1990 study representing units at the 15-year mark (1.0%) corresponded to the failure rates of the original 1980 study at the 15-year mark (1.2%) providing further validation of the findings of the first study.

The results of this study 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 (Canadian General Standards Board) 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 standard was 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, so it will no longer be considered part of the documentation for the current standard. One specific recommendation from the study was that ASTM 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.

The results of the survey also formed the basis for recommending to the U.S. Department of Energy the requirement to include insulating glass certification as a requirement for Energy Star Windows to address long term durability and energy performance. This recommendation is currently under review by both the U.S. Department of Energy and the National Fenestration Rating Council (NFRC).