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John Rarick

AGC Flat Glass North America

(404) 446-4234




Window Manufacturers Can Now Improve Window Performance By Up To 15 Percent

Alpharetta, Georgia, October 20, 2010– AGC Flat Glass North America has introduced a leading-edge glass technology called U4 4th Surface Technology™, which dramatically improves the performance and energy efficiency of double glazed window units without adding more glass panes. 

By adding U4 4th Surface Technology, double-glazed window systems are now able to achieve the same levels of efficiency as costlier triple-glazed units.  Traditionally, adding more panes of glass to a window was the only way to improve their performance and energy efficiency.  However, the U4 4th Surface Technology system has revolutionized the industry by incorporating a patent-pending pyrolytic low-E hard coating that can be installed on the fourth surface of an insulated glass unit (IGU).  This unique coating technology enables manufacturers to use two low-E coatings in one double-glazed unit, resulting in an R5-rated glass package in a double glazed unit.

“The demand for affordable window products that can reduce energy consumption and utility costs has never been greater,” says John Rarick, AGC Glass Company North America’s Marketing Manager, Building Products Group.  “Windows made with U4 4th Surface Technology not only provide homeowners and businesses with cost and performance advantages, but the energy savings positively affect the environment.”

 About U4 4th Surface Technology

Adding U4 4th Surface Technology to an AGC double-glazed IGU reduces the center of glass U-factor by as much as 20 percent compared to standard IGU configurations with one low-E coating.  More importantly, the U-factor reduction gained with a U4 glass package improves the whole window performance (Uw) by 16 percent when compared to a standard glass package.

            In standard double-glazed units with one low-e coating on the inside of the gap between the glass panes, the low-e coating permits the window to reflect solar energy outwards when the sun is shining and to reduce heat loss when it is cold outside. 

However, because there is no coating on the room-surface of the inner pane, some heat from the room is lost to the gap between the glass panes.  This heat loss can significantly lower a window’s thermal performance.  With the addition of the U4 4th Surface Technology coating to the room-surface of the inner pane (surface #4), the window is able to reflect energy to the inside as well as to the outside.  This reduction improves the overall insulating properties of a U4 IGU by as much as 15 to 20 percent over conventional IGUs.

Advantages Over Triple-Glazed Window Units

In addition to the energy performance advantages of U4 technology, the double-glazed system also eliminates many of the drawbacks of costlier triple-glazed window units.  First, the manufacturing process of triple glaze windows requires additional capital investments and new production processes.  By contrast, U4 technology can be easily integrated into current double glazed manufacturing processes.  In addition, the manufacturing cost of triple glazed IGUs is 50 to 60 percent more than the cost of adding U4 technology to a double glazed window.

U4 offers the performance and durability benefits of traditional pyrolytic glass products, providing an unlimited shelf-life with no performance loss.  U4 is easy to fabricate, requires no special tools, is extremely durable, and is easy to handle.  Moreover, it requires no edge deletion and can be tempered or heat-strengthened when needed.                                         

U4 4th Surface Technology is backed by industry leader AGC’s outstanding customer service and support, plus a 10-year warranty against cracking, chipping, peeling, flaking and deterioration.  To learn more about U4 4th Surface Technology, as well as other innovative AGC offerings, call (800) 251-0441 or visit

About AGC Glass Company North America     

 Through its three strategic business units, AGC Glass Company North America offers one of the industry’s broadest lines of Building Products, Solar Glass and Automotive Glass.  The company is part of Japan-based Asahi Glass Co., Ltd. – the world leader in glass production.  A fully integrated supplier, AGC Glass Company North America has more than 4,000 employees in its locations across North America.  To learn more, visit

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