Volume 7, Issue 8 - September 2006

Facts of Glass
Glass Manufacturer Discusses How Emerging Trends and Technologies will Affect Fenestration Manufacturers
by Fred Wallin

Perhaps no application category is growing faster today than the architectural glass marketplace. Since low-emissivity (low-E) vacuum coatings were first used to improve the thermal performance of architectural glass in the early 1980s, these coatings have achieved increasing acceptance in both the residential and commercial window markets—thanks in large part to the steady advances made in both coating materials and coating technologies in the past two decades.

As energy costs continue to skyrocket, low-E coatings will almost certainly continue to dominate both the residential and commercial marketplaces. So it is important for door and window manufacturers to gain a refresher course on the market (including energy labels) and new glass technology that may be incorporated into windows in the coming years. 

One Benefit of Rising Energy Costs
While all of us have suffered the negative effects of skyrocketing energy prices—whether in the home, at the gas pump, or in the workplace—most of us have benefited from the corresponding increase in the demand for energy-efficient low-E glass. 

Across the supply chain—from primary glass manufacturing to the coating line to the construction site—we have invested heavily in new coating capacity to support the sharp rise in demand for low-E glasses that improve energy performance. As buyers of both residential and commercial windows have become better educated about the bottom-line benefits of installing energy-efficient low-E products, vacuum-coated glasses have gone from a “niche” product to an architectural standard—in a decade.

Just how fast is the low-E architectural glass marketplace growing today? 

Currently, sales of low-E windows for the residential market are growing at a compounded annual rate of 19.5 percent. While this growth will slow as the market becomes saturated, low-E glass is expected to represent an 80-percent share of the residential market by 2008. 

The commercial construction marketplace was initially slower to embrace low-E glass coatings—but today, low-E products are growing at a compounded annual rate of 17.1 percent. By 2008, low-E should represent a 50-percent share of the commercial glass marketplace—and the good news is that this growth should continue, since this segment will not be saturated by low-E windows in the short term.

Effects of Labels and Lobbyists
As everyone from coaters to consumers sharpen their focus on energy-efficient windows, the demand for objective, third-party energy performance guidelines has risen dramatically. Those who make decisions about specifying, installing and paying for the “best” windows are increasingly looking for someone to define “best” for them. And a number of organizations have stepped forward to fill this role.

Today, the majority of windows marketed as energy-efficient in North America bear one or two labels—provided by the National Fenestration Rating Council (NFRC) and the Energy Star® window programs created by both the U.S. and Canadian governments. For example, 91 percent of wood windows include an NRFC label, and 57 percent display an Energy Star rating. Only 9 percent are not labeled.2 While all of us should applaud the efforts of these groups to educate window buyers, one problem is that these labels feature different performance data—and define the “best” windows based on widely varying standards. The result may be that consumers become even more confused about what is truly best for their own specific needs. Here’s a quick look at the window performance criteria used by several industry authorities:

  • The U.S. Energy Star windows program, created and administered by the Department of Energy, certifies windows based on two factors: U factor and solar heat gain coefficient (SHGC). It divides the country into four regions, based on annual heating and cooling needs, and attempts to address the primary energy usage in each area. For example, in the northernmost, coolest region of the United States, the energy used to heat homes is the primary concern. For this region, Energy Star recommends windows with a lower U factor—to minimize radiant heat transfer—and a higher SHGC, to capitalize on passive solar transmission. In the southernmost region of the country, Energy Star focuses on minimizing air conditioning costs, primarily by blocking solar heat gain.

  • By contrast, the Canadian Energy Star program, managed by the Office of Energy Efficiency, focuses on U factor and “heating degree days” (HDDs) when certifying windows. An HDD is the annual sum of the degrees of the average daily temperature, for all days below 18°C (64°F). The Canadian program logically groups the nation’s cities and regions together according to annual temperature trends, with the colder areas requiring more energy-efficient windows—and a lower U factor.

  • Window labels provided by the NFRC include U factor and SHGC, but also feature some newer measures such as daylighting, air leakage and condensation resistance. While this information may prove useful to a buyer, some performance criteria included currently by the NFRC may be misleading to buyers seeking the most energy-efficient windows on a year-round basis. One example is “daylighting,” or visible light transmittance (VLT). While a high level of natural light is an aesthetic choice that is becoming more popular in homes and offices—and is advocated by “green design” organizations—we all know that glass with the highest VLT levels often is not the most energy-efficient choice, especially in climates that remain warm year-round. While windows with high VLT ratings create bright, light-filled interior spaces, they can put a significant strain on air-conditioning systems in such regions, by also transferring excessive solar heat.

Why haven’t these three “objective” North American window authorities achieved agreement on their window ratings and recommendations? The answer is simple: all are subject to direct and indirect lobbying from industry coalitions, individual manufacturers, environmental groups, the scientific community and others advocating their own specific point of view. Charged with the task of not only understanding and interpreting the many nuances of window performance, but also balancing many special interests, it’s only natural that these third-party organizations would send mixed messages to the marketplace.

Adding to the confusion is the wide variety of state and local building codes that govern the residential construction marketplace. Not only are these building codes often at odds with the recommendations of the NFRC or Energy Star, but they also change constantly. Both professionals and consumers are expected to keep up with ever-shifting window standards. For example, in the wake of Hurricanes Katrina and Rita in late 2005, new building codes have been introduced along the Gulf Coast to govern both energy efficiency and hurricane resistance.

Overwhelmed with information, consumers look to groups, such as door and window manufacturers, even employees at big-box stores like Lowe’s and HomeDepot, for guidance in choosing the right window. But often these perceived experts are equally confused by the multitude of glass and coating choices available today.

A Shared Goal: Helping the Consumer
Where can the marketplace turn for a clearer view of window performance that takes a more scientific, consistent approach? Since glass manufacturers and coating professionals have partnered to create today’s range of sophisticated architectural glass products, I believe that we can play a role in teaching our customers, as well as the ultimate consumer, how to understand and differentiate among today’s dizzying array of window options. This is a challenging goal.

No one knows more about low-E architectural glass solutions than the people who manufacture and coat these products. I propose that we work together in the future to help consumers balance multiple performance criteria and navigate the latest market trends to arrive at not the “best,” but the most appropriate window choice for their own situation. Based on our shared insight into low-E products, we can help both commercial and residential decision-makers to choose appropriate windows based on many concerns, including year-round energy efficiency, as well as price, aesthetics, light transmission, privacy, glass color and other product attributes.

While this sounds like a daunting task, it simply means sharing our product knowledge with those across our supply chain, such as door and window manufacturers, and help you to navigate conflicting messages from different product labels, special interest groups and other sources of window information. 

For example, a recent trend in the architectural glass industry is minimizing ultraviolet (UV) light transmission, in order to protect fabrics and finishes from fading. The eventual goal of some segments of our industry seems to be to eliminate the transfer of UV light into interior spaces. This is the kind of topic that I believe we need to investigate together, working in partnership to come up with a realistic perspective. We need to ask and answer questions such as: Can we ever block UV light entirely? Given the antibacterial properties of UV light, is it healthy to pursue this goal? Should our industry instead support the development of more durable coatings for fabrics and interior finishes?

Today, an increased amount of attention is being paid to a new window measure called the light to solar gain ratio (LSG). This is a gauge of the efficiency of a glass product in transmitting daylight, while blocking heat gain. The higher the LSG, the more light is transmitted, without adding excessive amounts of heat. 

While many are heralding this as the “perfect” window performance measure, it has obvious limitations. Looking only at this number will not necessarily result in the most energy-efficient window, on a year-round basis, for a given region. 

New Innovations
Market-changing innovations will include variable-performance windows, including photo-chromic and electro-chromic glass solutions. While these coated glass products are available today, their current price point—up to $100 per square foot—needs to be reduced dramatically, to perhaps $10 per square foot, before they will win broad acceptance.

Other futuristic coated glass innovations could include:

  • Integrating television screens into windows, taking advantage of large bay windows and making them truly multifunctional;

  • Installing touch pads on coated glass surfaces, so windows can be used to control heating and air conditioning, security systems and even in-home audio components;

  • Designing photo-voltaic units into frit patterns, so large glass spaces such as atriums can be both beautiful and functional, generating valuable energy; and

  • Developing coated solutions with the same characteristics on either the second or third surface—including performance numbers, aesthetics, reflection, and transmission—for new levels of flexibility and efficiency.

In the ever-changing world of architectural glass, neither glass manufacturers nor door and window manufacturers can allow themselves to become complacent. Remembering the spirit of collaboration and innovation that led to the initial development of low-E coatings, we must agree to work together to achieve an even brighter future. Whatever next-generation solutions the future may bring, one fact is certain: we will arrive at them faster, more efficiently and more profitably if we work together. 

Note: Originally presented to the Society of Vacuum Coaters, this article has been adapted for door and window manufacturers.

Fred Wallin serves as vice president of marketing for AFG Industries Inc. 

1 Source: Ducker Research Co.
2 Source: The American Architectural Manufacturers Association. 

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