Volume 33, Number 5, May 1998


Fill ‘er up . . .

The art of Gas Filling for the Window and Insulating Glass Industies

by E. Carlton Douglas

Rampo's GompuGas is a 16-station gas-filling machine with four timers and a steel rack

During the 1970s, the Northwest corner of the United States instituted the toughest energy codes in the nation. The window manufacturers of the area were having a difficult time meeting the strict requirements of the codes until someone (many claim to have been the first) came up with a solution. The idea was to use a gas heavier than the atmosphere. It was agreed it would work because the whole theory of the manufacture of insulating glass is based on trapping air between two pieces of glass and sealing it so the air cannot escape. By this process, the atmosphere, which is made up of various gases (oxygen, nitrogen, argon, krypton, etc.), became the insulating agent of the unit.

Choosing a gas was fairly simple. Two gases, argon and krypton, have similar densities; however, the rarity and expense of krypton (up to 100 times more expensive than argon) made argon the clear choice.

Once argon was established as the gas of choice, the next obstacle was how to get the argon inside the insulating glass (IG) unit. Europe, which had an energy crisis ten years before we did, had already solved the problem. They sealed the unit as usual, stood it up vertically and bored two holes through the sealant and spacer—one near the top and one near the bottom. They inserted a probe in each hole. The top hole's probe was a sniffer. When the unit filled with argon, the sniffer would sense gas and shut off the machine.

Until the early 1980s, the only gas-filling machines available were from Europe and were of the sniffer method. At that time, Garry Wamsley of Insulate Industries in Auburn, WA, designed a machine that used the time/volume fill method. His machine, called CompuGas, was designed to calculate the time needed to displace the atmospheric gases with argon, again using a bottom hole, using pop rivets or some other device. This method assures the IG unit of being filled by more than 95 percent each time. Using the sniffer method, there was some doubt about filling the unit too fast or gas bouncing off grids, etc., causing a turbulence-like effect that could give an early false reading in the unit.

Most of the industry viewed this practice as crazy in the early years, but 30 years later up to 70 percent of window and IG manufacturing involves gas filling.

Gas filling became more sophisticated as time went by. Examples of this include machines with sniffers and the chamber method for bulk production. The Time/Volume Fill Method, however, remains the easiest and least expensive method used today. As gas filling progressed over the years, it was found that krypton was much more effective in small airspace applications such as triple glaze and Southwall Technologies' heat mirror product. By mixing krypton and argon in small airspace units, it is even possible to regulate the R-value. This value is dependent on the percentage of argon and krypton mixture. A typical IG unit with 11/16-inch airspace has an R-value of about two. Fill that same unit with argon and the R-value jumps to about three. If you add Low-E glass, that same unit will attain a four-plus R-value. A product called Super Glass, which is manufactured with one side Low-E glass, two heat mirror films and filled with krypton, can reach an R-value of ten. The latest experiment to appear on the scene is xenon. Results are not conclusive yet, but the cost of xenon is five times greater than krypton. Although the price would make this appear cost prohibitive, who knows? Thirty years ago, the use of any gas filling was thought to be crazy.

The benefits of argon in the gas filling industry have provided the manufacturer with a valuable sales tool in upgrading customers to a better window. In addition, the National Fenestration Rating Council is presently setting a minimum standard that all window manufacturers will have to meet. To achieve the minimum standard, it appears that gas filling will be required in all windows.

USG E. Carlton Douglas is president of Ramapo Sales & Marketing, Inc./CompuGas in Oakland, NJ. He has been in the fenestration industry for 25 years.

Copyright 1998 Key Communications, Inc. All rights reserved. No reproduction of any type without expressed written permission.