The Insulating Glass Manufacturers Alliance (IGMA) held an open-panel seminar Wednesday called “Glass Performance for Energy-Efficient Fenestration.” The panel was moderated by Bill Lingnell, technical consultant for IGMA. Chris Barry, director of technical services for Pilkington NA, and Jeff Haberer, mechanical engineer for Cardinal IG, served as lead members in the discussion. The panel was held as part of IGMA’s Educational Seminar, held over the last two days at the Las Vegas Hotel and Casino in Las Vegas.

Topics discussed in the panel included thermal stress and solar absorption, as well as low-E coatings.

Lingnell asked about the work currently done with low-E coatings on a number-four surface.

“Is there work going on with the fourth surface? Yes. Are we offering it on a long line of products yet? No. We have more to worry about than just U-factor,” said Jim Krahn, advanced research manager for Marvin Windows and Doors. “When you put a coating on the fourth surface you change the equation.”

Condensation on double-clear windows was also a debated topic. When questioned about winter-time condensation in Canada, Barry offered both an explanation and solution.

“There’s your temporary condensation and your long-term condensation,” said Barry. “What is an important issue is any long-term condensation that stays there. It rots out the spacers, the wall [and] the wall unit. That must be prevented. You will get condensation any time the temperature falls below the dew point of the air. On a temporary basis this is okay, on long-term basis, we must not have it. We do not get condensation on properly made half-inch clear double-glazing windows under normal residential and commercial conditions.”

“I think we need to understand fourth-surface coatings fully before we implement it fully,” added Krahn.


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