March - April 2003

The Cutting Edge

To Fill or Not-to-Fill...
That is the Question
by Jim Plavecsky

Argon filling is becoming quite the controversy lately (see DWM April-May-June 2002, page 36). Before the arrival of the Gas-Glass instrument, it was easy and convenient for many window manufacturers to argon fill. This was because they had no real concern about how much argon really filled the unit or even how long it would stay in the unit. But now, with the advent of an accurate and repeatable quick-check method, combined with new Harmonized Insulating Glass Standards, many manufacturers are doing a double take when it comes to argon filling. 

Production Concerns
The first thoughts that enter the minds of manufacturers are: “If I am going to claim that my windows are argon-filled, I better make sure that each and every unit that goes out the door has some minimum and acceptable level of argon in it!”
 

Contiguous Corners   Metal Corners   Plastic Corners When fabricating an IG unit, using a design that enables a continuous framing system is highly recommended.

At the same time, the increasingly competitive market dictates that this be accomplished in the most cost-efficient manner possible. This is where advanced technology comes into play. Ensuring consistent fill rates does not necessarily have to translate into a slower production process and consequent higher production costs. Manufacturers of gas-filling equipment now are offering equipment capable of much faster and consistent fill-rates as well as automated methods, which can take incremental labor out of the picture altogether!

At the same time that we are concerned about adequate fill rates, we also need to be concerned about insulating glass assembly techniques. When it comes to argon gas retention, quality assurance takes on a whole new meaning. Minute flaws at the bond-line interface of an IG unit may not always result in a callback because, even if a higher level of moisture vapor is entering the unit, there is this wonderful powder called desiccant waiting inside the spacer to adsorb it. The IG unit may fall short of its designed life expectancy, but if it is only a small flaw and there is an adequate amount of desiccant, the unit may still last beyond the warranty period. Of course, this depends on how long of a warranty is offered. However, when it comes to argon leaking out of the unit through these same flaws there is no saving grace on the other side of the glass. Argon is going to escape from the unit and there is nothing that is going to help prevent this from detracting from the advertised thermal performance of the 
window system.

Design Considerations
When it comes to unit design, there are several factors to consider. Be sure to compare the argon permeability or permeance rate of the various IG sealants under consideration. The values will be listed in grams per square meter per day, and the lower the number, the better. For example, polyurethane sealants have permeance values around .20 whereas the new dual-seal equivalent IG sealants have permeance values ranging from .07 all the way down to 0.00006.

Another important design consideration is the IG framing system. Conventional corner keys are 
usually a problem area. These must be crimped carefully and can sometimes work themselves loose as the unit expands and contracts. This can result in the formation of a void, which then becomes a leak area. For this reason, a continuous framing system is best. This can be achieved by a bending spacer or using a continuous spacer system. 

Lastly, sealant application behind the spacer is critical as well. Make sure the glass is cleaned properly. Follow the sealant manufacturer’s process guidelines to achieve proper flow rates when gunning or extruding. This is critical to achieving consistent adhesion at the bond-line interface, where argon is trying to escape. Improper flow rates or gunning techniques can result in cold joints, which can result in much higher leakage rates than otherwise would be allowed based on unit design.

The bottom line is that if you want to make sure you are putting the correct amount of argon in the unit, the costs associated with a higher level of quality are going to be a much bigger concern than the cost of the argon itself. For this reason, many window manufacturers are choosing not to gas fill and are instead opting for the highest-performing warm-edge products. 

“I would rather get my U-value by using the best warm edge and without argon because I can see that it is in the window and I know that it is not going anywhere,” said one window manufacturer.

Whether choosing to argon fill or not, one thing is for certain: window manufacturers are being faced with a consumer market in which buyers are much more informed than ever. Argon filling can offer significant advantages when it comes to improving the overall thermal performance of the window system. But if you are going to do it, you had better do it right! 

Jim Plavecsky is the owner of Windowtech Sales Inc., a sales and consulting firm specializing in the 
window and door industry.

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