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May  2004

The Cutting Edge

HIGS—Here at Last!
North American Insulating Glass Durability Standard Finally a Reality
by Jim plavecsky

Canada and the United States have finally come together with a harmonized insulating glass or “HIGS” test standard for evaluating insulating glass durability. Canada has the CGSB or CAN 12.8 test and the United States has the ASTM E-773/774, commonly referred to as the “CBA” test. This year, one has the option of running the CGSB, the CBA or the HIGS test. By next year, HIGS will be the only option. So, the time is upon us to take a look at HIGS to see just what it will take to make the grade. 

A Tougher Test
There are two key differences that make the HIGS test tougher than the CBA test. One is the dew point requirement and the second is the volatile fog test. The dew point requirement to pass the CBA test in Class C is –30 degrees F (-34 degrees C). To pass Class B it is then raised to –20 degrees F (-29 degrees C) and is again only –20 degrees F to pass Class A. However, when running HIGS, the dew point requirement is the same as used in the Canadian or CGSB test standard, -40 degrees F or –40 degrees C. 

This means the insulating glass sealant must be doing a better job of inhibiting the infiltration of moisture vapor and the desiccant must be fresh so that it is operating at peak capacity.

Workmanship becomes key. Tiny cavities on the bond line interface or cold joints at the corners can have dire consequences. The proper desiccant type must be chosen and it must be fresh, keeping proper storage procedures in mind. 

The other piece of the HIGS test that makes it tougher than the CBA test is the volatile fog test, which must be done on several units using the fabricator’s low-E gas. The CBA test only involves low-E in cases involving the use of non-edge deleted soft-coat products, but HIGS does not differentiate. The volatile fog test is designed to turn any impurities trapped within the insulating glass unit into a gas, therby allowing the formation of a chemical fog withing the unit. The tough part is that this chemical fog shows up much more readily low-E glass than it does on clear glass.

Another aspect of the HIGS test that makes it even tougher than the CGSB is the viewing procedure 
surrounding the volatile fog test. The CGSB test calls for the IG unit to be mounted in a viewing box and for the evaluator to stand 2 meters in front of the test unit. A failure is indicated by the presence of a fog at this distance viewing the unit from a frontal position only. In contrast, the HIGS test involves viewing the unit from an “arms length” and fog may be observed from any angle. This makes it easier to fail the unit, even though the unit is heated to only 122 degrees F versus 140 degrees F in the CGSB.

Eliminating Failures
According to John Kent, administrative manager for the Insulating Glass Certification Council’s program, the percentage of failures has been higher than normal in the last few years, and many of these failures occurred in the volatile fog portion of the test. 

Indeed, many new IG components have hit the marketplace recently. There are so many new glass options, warm-edge spacers and new sealant entries. Some of these components are designed to make our windows warmer, and some are designed to make 

our windows more affordable. However, we must never forget that insulating glass durability must never be compromised. It must always be kept on the front burner. After all, what good is a window if one cannot clearly see through it?

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