Accelerated IG Testing
Ensuring a Clear View for Years to Come

by Jim Plavecsky

The last 15 years have been dynamic in the window industry. We have seen the entry of new materials such as vinyl frames, thermally broken aluminum frames, wood composites, warm-edge spacer systems, low-E glass and argon/krypton gas fills. These are all designed to add and enhance the thermal performance of window systems. 

With the entry of all of these new materials and thermally improved systems, however, window manufacturers must not forget that value is also derived from durability. The newest designs and materials should be evaluated fully to make sure they are capable of providing long-term, trouble-free performance. Homeowners should not expect to be faced with replacing insulating glass (IG) units, or even windows themselves, only five years after moving into a new home. The same applies to replacement windows, which represent a considerable investment for a homeowner wishing to upgrade older windows or replace defective windows in an older home. 

Weather Cycling Tests
One approach is to conduct accelerated weather cycling tests in accordance with a certified test method. Certification programs such as those offered by the National Accreditation and Management Institute Inc. and the Insulating Glass Certification Council are available to IG fabricators as a standard method of certifying the quality 

Harmonized Insulating Glass Standard Accepted by NBCC
The Insulating Glass Manufacturers Alliance’s (IGMA) request to change the National Building Code of Canada (NBCC) to reference ASTM E2190 has been accepted by the Standing Committee on Houses for the NBCC and will be referenced in the 2005 version. Ray Wakefield of Trulite Industries and Marg Webb, IGMA executive director, went before the committee on October 19 in support of the change. IGMA expected to receive formal notification from the National Research Council in late December 2003.

“This is an important development with benefits for IGMA, our members and the North American insulating glass industry,” said Oak Moser, IGMA president. “Manufacturers will now be able to certify their product for both sides of the U.S./Canadian border using a single, certification agency.”

While the change will be reflected in the 2005 edition of the NBCC, IGMA says it has been advised that many code officials will accept the new reference immediately based on the strength of the standing committee’s 

In addition, Wakefield and Webb have been approached by an official from the Ontario Building Code (OBC) to include the new ASTM reference in the provincial code. IGMA will provide the code development and interpretation unit for the Province of Ontario with the same information that was provided to the NBCC standing committee, as well as some specific information relating to the Ontario marketplace. 

and durability of IG fabrication methods. The United States and Canada have been working for years to develop new harmonization standards for insulating glass. These new Harmonized Insulating Glass Standards (HIGS) have been approved by the ASTM E.06.22.05 Sealed Insulating Glass Committee, and the new test standards, ASTM E2188-E2190, are now in place. As of spring 2003, window companies may choose either the ASTM E773/E774/E1887 or the new HIGS standards.
 For those companies marketing products in both the United States and Canada, it is beneficial to test to the HIGS standards.

The ASTM E-773/774 was once the subject of a 15-year field correlation study conducted by the Sealed Insulating Glass Manufacturing Association (precursor to the Insulating Glass Manufacturers Association). Actual field installations of C, CB and CBA rated units were tracked and observed for years to see how long each would last before internal fog appeared. The conclusion of this study was YES—success in accelerated weather cycle testing does indeed correlate with field success.

So why don’t more window manufacturers participate in this certification process? By my last estimate, it looked as though only about one in five window manufacturers utilize one of the certification programs for sealed IG durability. On top of this, many of offering ten and 20-year warranties on the IG units installed in their windows. How dangerous is that?

Stringent P-1 Tests
At the other end of the spectrum, there are window manufacturers who believe the ASTM tests are a minimum when it comes to accelerated testing of IG units. Many of these companies employ a much tougher test method, commonly known as the P-1 Test or modified P-1 test, which is extremely tough on IG units. It is a sealed chamber into which the unglazed units are placed. The conditions are 140° F, 100-percent relative humidity and constant ultraviolet (UV) bombardment from high-intensity lamps and must be fog free at –40° F or lower. These conditions accomplish several things. The heat in combination with the UV ages polymers, destroying the elastic nature of the edge sealant. It also breaks down the chemical bonding between the sealant-spacer and sealant-glass. The result is a faster level of moisture vapor entry into the IG unit. As moisture vapor enters the unit, the desiccant adsorbs it. Once the desiccant is saturated, the unit fogs. It is commonly believed that for every week an IG unit lasts in the modified P-1 test, it will last a year in the field.

Smart window manufacturers will employ these methods of accelerated testing to estimate and build durability into their IG unit designs while also assuring the quality of fabrication methods. The certification ratings and test reports can serve also as marketing tools to let the consumer know that these windows incorporate technology designed to withstand the test of time. The homeowner can then rest easily knowing that the warmest view will also be the clearest view for years to come.