Volume 2   Issue 3               Fall 2001

T h e  C u t t i n g  E d g e

Spark of Hope Ignites the IG Industry
by Jim Plavecsky

Argon gas retention is gaining a lot of attention lately. Because argon has lower thermal conductivity than air, window manufacturers can fill the space between lites of glass with argon thereby improving overall window U-values. In some instances, this can make the difference between complying versus not meeting a U-value code. For replacement windows, it can make the difference between getting or not getting the order, especially if the competition offers gas-fill and you do not!

However, the practicality of keeping the argon within the insulating glass unit (IGU) over its useful life is of concern to many. In recent years, window manufacturers have discovered that argon escapes from an IGU at a rate faster than oxygen, nitrogen and carbon dioxide can re-enter the unit to replace it (see figure 1). This is due to what scientists refer to as the Law of Partial Pressures. Therefore, over time, the IGU begins to develop a negative pressure between the lites of glass. This leads to unit deflection, which in turn creates stress on the sealant bond-line, which can result in either adhesion failure or stress cracks and necessitate replacement of the IGU. The unit also is concave (see figure 2), which causes visible distortion. Homeowners look through their windows and everything looks blurry—not to mention the fact that if argon does not stay within the unit, the added thermal benefit originally claimed by the window manufacturer is no longer there for the consumer! The result is a call to the window manufacturer, who now has a warranty claim on his hands.

The industry has several methods to measure how much argon is inside an IGU. One of the most accurate procedures involves sampling the gas within the unit using a gas-tight syringe. The syringe is used to penetrate the IGU through the back side. The inside air space is accessed, and a sample of gas is taken into the syringe. The actual argon content of the sample is then determined using gas chromatography (GC). The advantages to this method are that it results in an accurate and repeatable measurement. The major disadvantage to this method is the integrity of the IGU may be compromised since the syringe penetrates through the IG spacer/sealant system. A septum has been developed that can be sealed into a hole, drilled through the spacer system. This involves changes to the construction of the IGU. The ideal method would be to measure the argon content within the IGU nondestructively with some external and portable device capable of measuring argon content without any changes being made to the unit.

Sparklike Ltd., a Finnish company, has developed just such a device (see article on page 58). The company’s GasGlass device creates a high-frequency, high-voltage, low-current spark, sort of like a window stun gun. The spark is applied from one side of the IGU to ignite a plasma inside the window, but only if the concentration of argon inside is more than 50 percent. The degree of intensity of this atomic emission or plasma light is measured, and an exact concentration of the gas inside the window is thereby calculated. Sparklike claims an accuracy level of plus or minus 1 percent. A single measurement takes less than two seconds, but perhaps the neatest thing about the GasGlass is it is highly portable. It can be used both inside the window manufacturing facility as a quality assurance tool, and it can just as easily be taken out into the field to evaluate real-world performance or to validate warranty claims.

“Perhaps the neatest thing about the GasGlass is that it is highly portable. 
It can be used both inside the window manufacturing facility as a quality
 assurance tool, and it can just as easily be taken out into the field to evaluate 
real-world performance or to validate warranty claims.”

Update on ASTM Task Group E 06.22.05

ASTM task group E 06.22.05 is working on putting together test methods and specifications for the Harmonized Insulating Glass Standard (HIGS). The HIGS standard is a proposed test standard to replace/combine the current ASTM E773/774 and the CGSB 12.8 M-97 test standards. 

In addition to test standards for unit durability and fog resistance, the group is also working on developing a standard method for testing argon content in an IGU. So far, existing work has focused upon using the GC method in addition to an Oxygen Analyzer Method, which also involves sampling the gas within the IGU. However, not surprisingly, Sparklike’s GasGlass has recently caught the attention of this group as well. 

While most of the other documents are almost ready for submission to the subcommittee, a suggestion was made to work on drafting an ASTM test method to non-destructively measure the argon content in an IGU using the Sparklike equipment.

Edgetech IG and Cardinal IG are testing the prototype version of GasGlass. Readings obtained from GasGlass were compared with readings obtained via a GC. Accuracy of GasGlass has been reported to be within +/- 2 percent, when compared with the GC.

A lot of work needs to be done on the GasGlass, but it is drawing tremendous interest from the fenestration industry. For years, argon gas-filling has been the topic of much controversy and speculation, mostly because many do not believe IGUs are capable of containing the argon to provide the energy benefit over the course of time. Those holding this belief are reluctant to offer argon-filled windows for fear of possible consumer complaints or even lawsuits, which might arise from the negative deflection issue or the loss of thermal benefits claimed by the manufacturer originally. The GasGlass and similar devices could be the tools for which the fenestration industry has been waiting to help establish the credibility of argon filling as a real, long-term benefit to the window consumer. 

Jim Plavecsky serves as vice president of marketing and sales for Edgetech IG, based in Cambridge, Ohio.


DWM
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