Volume 10, Issue 2 - February 2009

Trouble with Triples
Weighing the Cost and Benefits of Building Triple-Glazed Units
by Mike Burk

Triple-glazed insulating glass (IG) units or “triples” are a popular topic these days. Triples promise improved energy savings, a high level of condensation resistance and higher profit margins. They often pop up as manufacturers determine manufacturing methods to meet upcoming Energy Star® and National Fenestration Rating Council (NFRC) codes. 

Fenestration industry suppliers offer components and equipment that will ease the manufacturing process and build a better window. Environmental groups fill websites with descriptions of how carbon footprints can be reduced with the use of triple-pane glass. The word is out, but not everyone agrees. The line in the sand seems to be well established. Either you love them or hate them. There seems to be little in between.

A survey conducted by the NFRC confirms that, of all the factors homeowners consider when thinking about new windows, energy performance is by far the most important. Almost every one of the respondents, 97 percent, said energy performance was an “important” or “very important” factor in their window-buying decision.

With this information, the question has become: Why not build triples? They do improve energy efficiency dramatically when constructed properly—an important value-add to customers.

The Drawbacks?
After a careful review of the websites of a number of manufacturers, problems conveniently outweigh the benefits for some manufacturers not producing triples currently. Some of the drawbacks these manufacturers cite for building triples include: 

• Higher costs for consumers and manufacturers;
• Decreased light transmittance and a muddled view to the outside;
• Increased glass weight, resulting in a need for larger frames with a bulky appearance;
• Lowered R-value because of the conductive metal frame support;
• Decreased glass size, resulting in a smaller viewing area through glass;
• Increased threat of building safety violations because of reduced glass area/reduced window egress; 
• Higher risk of glass seal failure; and
• More difficult operation.

However, even some anti-triple fabricators can come up with a couple nice things to say. One manufacturer’s website says that triple-glazed units improve the center of glass and improve energy efficiency “marginally.” Consumers also are urged to “do their homework” before making decisions on doubles versus triples.

The Benefits
Consumers, manufacturers, test facilities, environmental groups and government regulatory agencies have done their homework; and they do not agree.

We believe that many consumers have found that although windows with triple-pane glass are more expensive, the energy savings is worth the investment. Triple panes reduce heat transfer and can help decrease energy usage and energy bills. 

Research by a door and window manufacturer shows that triples offer dramatically better condensation protection and 60 percent more energy savings than double-glazed units with low-E coatings and argon filling—at a cost that is only five percent higher. 

Additionally, in fenestration products sound transmits more or less readily depending on the unit’s density, stiffness, mass per unit area, temperature and air leakage. Because triples increase density, stiffness, mass and temperature and reduce air leakage, it stands to reason that triples improve sound transmission through the system. In areas where noise is an issue—such as near airports or busy streets—triple-pane glass with certain spacer systems provides added sound dampening ability. In fact, many hotels near airports market their triple-pane glass as an added value that provides patrons a quiet and restful stay. Another manufacturer boasts that its high-end products are almost exclusively triple-pane because:

• A window with three panes is an investment, not just a purchase, because of long-term energy savings; and
• Triples offer condensation resistance and energy savings at modest incremental costs.

To establish this point further, the U.S. Department of Energy mentions on its website that although “efficient windows will add cost; they also provide tremendous value in comfort, durability and energy savings. They may also lower peak loads for heating and cooling a home, which allows for smaller heating, ventilating and air conditioning equipment.”

It really doesn’t matter which side you are on; everyone agrees that triple units save energy. Manufacturers of windows need to respond to this opportunity. If you are considering adding triples to your insulating glass facility, you need to consider the different production operations to build these units properly. If you manufacture triples presently you may need to revisit your production process because manufacturing triples involves much more that stacking a third lite of glass when done appropriately.

Analyzing Your Processes
Like any new product, the new triple must start in the design phase. Glass type, glass thickness, coating selection, airspace, overall unit thickness and gas fill requirements must be defined. As mentioned previously, the triple will weigh more than a double-glazed unit. The weight should be determined by factoring in all components, including glass and spacer materials. Check the capacity and limitations of the balances, hinges and operators. Review the rigidity and strength of sash materials and consider alternative sash materials, such as composites or fiberglass. One manufacturer limits the size of casements triples with glass to 30 inches. For larger units, this company utilizes suspended films or opening restrictors. A well-planned, quality design will produce triple-glazed windows that are easier to operate than many double-glazed windows.

The next step is to involve the IT department. Your business operating systems may need updated to specify and process triple-glazed windows. The sales staff will require training on glass coating options and order entry procedures for triple-glazed units. The machine interface software may also need adjusted or updated. The system will need to recognize the glass size, thickness and coating for the additional lite. Glass inventory locations, minimum stock levels and cutting table optimization software will need to be checked or adjusted as well.

The associates of the glass cutting department will require training in loading, handling, separating and sequencing the lites. Breakout monitors and slot sorting rack procedures may change, and the addition of different glass coatings may change the current edge deletion policy.

Triples allow for more glass coating surface options. There are now six surfaces that might be coated and require specific orientation. The washer operator may need to review the washer loading sequence and glass surface orientation to ensure uninterrupted production. Since the center lite of the triple must be perfectly clean and dry on both surfaces, flipping the top lite to move dirty or contaminated surfaces to the outside of the unit is no longer an option. Proper glass washer operation is now more critical. Glass lites exiting the washer must be clean and totally dry on both surfaces. Preventive maintenance of the washer must be completed on a regularly scheduled basis.

There are presently spacer systems available that suspend the middle lite as the units are assembled. Other spacer systems will require an additional spacer to complete the unit. If the units are assembled manually, the operators or stackers must be trained on new stacking procedures. These procedures should identify which air space will contain the grids or muntins, as well as the coating orientation. Some automated assembly systems will recognize the triple unit and process the entire assembly. Other automated systems may require operator intervention to insert the third lite of glass or second spacer.

The sealant system and application method must be reviewed. Automated dual-seal units may require machinery operation programming changes or mechanical adjustments. Units that are manually sealed or hand-gunned may require additional caster tables or handling devices. Hand-gun tips may need to be replaced or modified.

Units assembled using single-seal hot-melt materials and heating and compression sections should be inspected and evaluated. Care must be taken to assure that the sealant temperature, especially between the spacers and glass surfaces three and four, reach the required glass temperature for proper spacer adhesion.

Gas-filling procedures must be defined to determine if both air spaces or a single air space is to be filled. In the case of a single air space filling, the correct air space must be determined. Gas fill probes or lances may require replacement or modification to fit the smaller air spaces common with triples. Also keep in mind that storage racks, harp carts may require modification to handle the thicker units safely.

The requirements for testing and certification must also be reviewed. For example, the Insulating Glass Manufacturers Alliance (IGMA) has proposed the required testing of triple-glazed units every four years for IGMA and the Insulating Glass Manufacturers Association of Canada programs, and the testing of double-glazed units for the intervening years. Check with your third-party certifier for triple-glazed requirements.

Meeting Today’s Demands

There is a lot involved with properly adding triples to a product mix. Some may think that it’s just not worth all this effort. Maybe that’s why the manufacturers at the beginning of this article listed so many disadvantages with triples. Adding triples is almost like starting from scratch in terms of design and production.

But it is worth the effort. The triple-glazed unit is not the window of the future; it is the window of today with increasingly stringent energy codes and the customer demand for optimal energy efficiency.

As manufacturers, now is an ideal time to begin offering these energy-saving products to your customers. Chances are the slow economy has slowed your production. It is a great time to modify your assembly area to produce triple-glazed product. Don’t allow your competition to get a head start. 

Mike Burk serves as product manager for Edgetech I.G. He may be reached at mike.burk@edgetechig.com. Mr. Burk’s opinions are solely his own and do not necessarily reflect the views of this magazine.

DWM
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