by Marc Massa
The worldwide energy crisis in the early 1970s changed the glass industry forever, as architects, builders and homeowners began to look beyond the appearance of windows and consider the profound effect that glass coatings and window designs can have on annual energy costs. In both residential and commercial applications, consumers began looking for a reliable measure of energy efficiencyas well as a way to differentiate among the relatively limited selection of products available. The glass industry introduced a number of innovative technologiesincluding high-performance reflective coatingsto answer the new need for energy-saving products.
As the global economy improved in the early 1980s, concerns about energy efficiency remained, and glass manufacturers continued efforts to develop innovative technologies and processes that would maximize window performance.
Low-emissivity coatings were one of the biggest developments in the flat glass industry during the last decade. "Low-E" coatings enable homeowners and commercial architects to cut heating costs by reflecting radiant furnace heat back into the buildings interior. In addition, these coatings reduce condensation levels by increasing the glass temperature.
Today, low-E glass is more readily available than ever beforeand is widely used in both new construction and replacement windows. In fact, research conducted by AFG Industries indicates that low-emissivity glass is used in 37 percent of new starter homesand in 61 percent of luxury homes. It is also widely used to maximize year-round energy efficiency in commercial buildings across North America.
During the 1990s, glass manufacturers have responded to the ever-increasing demand for low-E glass by developing and marketing a wide array of products, with different coatings aimed at achieving different performance characteristics. However, the wealth of product options in the marketplace today means consumers are still faced with energy-efficiency measures and performance factors that are often confusing.
The truth is, the modern window marketplace is confusing for a good reason: There is no single product that is best for every application. Instead of shopping in a "one product fits all" marketplace, consumers can choose from a plethora of good products and a variety of energy-efficient solutions based on what is right for their needs. While this is an obvious benefit for both the glass industry and consumers, it can make choosing the "best" product rather complicated.
In order to ensure that customers are using "low-E" products effectively, glass manufacturers and window fabricators need to educate homeowners and commercial architects about energy-efficiency issues. Customers need to understand that choosing the "best" window is based on their own unique climate, annual BTU requirements, and aesthetic considerationsinstead of universal energy-efficiency standards that may govern their selection of other products.
For example, passive solar energy is a "free" energy resource that can reduce heating costs during winter monthsand consumers in northern areas should choose glass products that permit maximum solar heat gain. In these cooler climates, pyrolytic low-E products block 71 percent of radiant furnace heat from escaping a building in winter, while allowing 72 percent of available solar heat to enter.
While pyrolytic products traditionally have been viewed as better suited to northern regions, new technologies enable sputter-coated products to achieve high solar heat gain coefficients as wellmaking them energy efficient in these areas.
Conversely, consumers in more southern regions should select glass products that minimize solar heat gain, to keep annual cooling costs low. Generally speaking, sputter-coated glass products block more solar heat than pyrolytic coatings, making these products ideal for areas with warm temperatures year-round. But, again, technology innovations enable pyrolytic products to perform well in these regions.
A basic rule for consumers to remember is this: In northern climates, high passive solar heat gain ratings are important, while products with lower solar heat gain ratings are better suited to southern regions. Low-E ratingswhich reflect heat transfer rates between interior and exterior spacesare desirable in all areas of North America.
With the wide array of energy-efficient, low-E products available, consumers have never been in a better position to make smart choices and lower their annual energy bills. We in the glass industry need to communicate the differences among products, and ensure that builders, architects, and homeowners understand how year-round efficiency is truly achieved.
While many industries have adopted universal standards and can endorse clear-cut performance measures, the glass industry needs to recognize the differences among different regions and varying climatesand help end-users make intelligent product choices. The good news is that with the wealth of products available today, every consumer can achieve maximum energy efficiency and benefit from the highest-quality glass products ever available.
Marc Massa is director, product sales and marketing for AFG Industries in Kingsport, TN. With nine manufacturing facilities located across North America, AFG is one of the few manufacturers that provides both pyrolytic and sputter-coated products.
AFG Industries recently launched Comfort TiŽ low-E glass. This new sputter-coated product uses a base coat of ultrahard titanium to achieve record-low emissivity ratings and excellent passive solar heat gain rates. The company says the glass is a particularly good choice for residential windows and patio doors in northern climateswhere it helps maximize furnace efficiency during colder months. It adds that Comfort Ti is a product of the "Twin Mag" process, which achieves superior hardness and thermal performance.
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