Volume 34, Number 3, March 1999


Efficiently Choosing a Window

by Tara Taffera

With consumer confusion over the meaning of U-factor and SHGC, USGlass analyzes the rating systems and determines what changes the industry feels need to be made. But it won’t be easy.

Industry experts have described the process by telling you what it is not. "It’s not as easy as buying a refrigerator." "You can’t look for the yellow label found on most appliances citing the amount of BTUs." "It’s not as easy as the miles-per-gallon system for an automobile."

The "it" being referenced is the way in which consumers determine the energy efficiency levels of windows for their home. So why is it so easy for consumers to determine the value of household appliances, or to determine how many miles-per-gallon their automobile will consume, but so difficult for them to choose the most energy-efficient windows for their home?

Some industry experts say the reason is because consumers don’t understand the meaning of information with which they are provided such as U-factor and solar heat gain coefficient (SHGC). Rating systems, such as those provided by the Department of Energy’s (DOE) ENERGY STAR® label and the National Fenestration Rating Council (NFRC) are in place. Most glass manufacturers agree that these approaches are a great first step, but a more consumer-friendly rating system should be devised. Sounds easy. But getting all interested parties to agree on this new system is not a simple task.

NFRC Rating System

NFRC, a non-profit, public/private organization based in Silver Spring, MD, developed a uniform national rating system for energy performance of fenestration products, including windows, doors, skylights and similar products. NFRC was formed in the late 80s when manufacturers, glass suppliers and code officials came together to develop procedures for testing, certifying and labeling windows. Prior to this time consumers had no way to compare products. "Now all products are simulated, tested and labeled in the same way," said Susan Douglas, NFRC administrator.

To participate in the certification program, a manufacturer must submit a product to be certified for one or more of the NFRC rating procedures. NFRC-certified windows have a temporary window label that can list three energy related factors: U-factor (a measure of heat loss, also known as U-value), solar heat gain coefficient or SHGC (a window’s ability to block warming caused by sunlight) and visible light transmittance (how much light gets through a product).

Currently, NFRC requires that only the U-value performance measurement be listed on an NFRC label. "The membership thought this was the most important," said Douglas. At their option, some window manufacturers do place the SHGC and visible light transmittance performance measurements on the label.

The process is relatively simple. Glass manufacturers submit full spectral data, including emissivity characteristics, for all products to the NFRC. That information is presented in a peer review process where other manufacturers are able to study the numbers and determine if they are accurate. Window manufacturers and testing labs use that data in simulations to analyze the performance of a product. The test procedure then validates the simulations and the window manufacturer is authorized to use that performance rating.

During the four-year cycle, a product also is shipped from the manufacturers production line to a test lab (this must be done by every plant producing products with an NFRC label).

"We believe that a large portion of manufacturers are in the NFRC program," said Douglas. "All major manufacturers participate and more of the regional manufacturers are getting involved as they see the value of the program." Douglas added that she is extremely proud of the NFRC program. "It is wonderful to see these groups come together to produce a solid procedure based on good science," she said. Others agree. "These are scientific facts you can’t dispute," said Mike Curtis, manager of the regulatory communications group at Cardinal IG, based in Minetonka, MN.

These procedures are aimed at achieving the NFRC’s foremost goal: to educate the consumer, an objective with which others agree. "Our goal is to have 90 percent of windows NFRC labeled," said Sam Taylor, manager of windows and glazing research programs for the DOE in Washington, DC. "Consumers can’t tell the difference without it."

The NFRC continues to conduct research concerning energy efficiency and is working on ratings for optical properties (which will study UV and glare), condensation resistance, long term energy performance and seasonal heating and cooling ratings. Also, the NFRC recently completed development of a procedure to accredit labs to now test for air leakage.

Criticisms of the NFRC Rating System

While only the U-factor is required on the NFRC label, many in the industry believe other factors should be included as well. "U-values are only half the story," said Paul Gore, residential products manager for Pilkington LOF, based in Toledo, OH. "We’re pushing the industry to use solar heat gain as a means of evaluating energy performance for a window. A high SHGC combined with a good U-value performs best in a heating-dominated marketplace," he said. "U-factor is okay for heating-dominated climates but it doesn’t represent cooling-dominated climates," said Curtis.

Tim Singel, coated products manager for Guardian Industries Corp., in Auburn Hills, MI, also does not believe U-factor is an accurate predictor of energy efficiency. "Ideally, the information listed on a label would provide the consumer with an answer to the question of energy efficiency," said Singel. "Realistically, the information on a NFRC label will only provide the consumer with thermal-optical performance potential." Singel said that until the context of home design, orientation and owner lifestyle are applied, the values are fairly meaningless.

Singel believes part of the communication problem starts with the mission of the NFRC. "The NFRC is a technical forum," he said. "It is difficult to task a technical group with the responsibility to distill a complex issue into an easy to digest consumer-oriented package."

To help make it easier for the consumer, the NFRC developed a special brand awareness subcommittee to determine what the consumer wanted to see on a NFRC label. Pat Kenney, marketing manager of flat glass products for PPG Industries, based in Pittsburgh, PA, led this committee.

Kenney said that when an outside consultant conducted a study to determine what the consumer wanted, it was found that the consumer desired to receive information from a variety of sources. "They want it [information related to energy efficiency] to be simple to understand and credible," said Kenney.

"What they really want is a miles-per-gallon system," he said. "But the NFRC is not in a position to provide that today."

ENERGY STAR Windows Program

While NFRC has developed a standard way of rating windows, the DOE’s ENERGY STAR program took it a step further by prescribing the parameters that define a high-performance window. Douglas compared the NFRC rating system to the Intel chip inside a person’s computer. "We provide the standard then we leave it up to the DOE and other groups to decide what they will do with the label," she said.

ENERGY STAR Windows, launched in March of 1998, is a voluntary partnership between the DOE and the fenestration industry to promote sales of energy-efficient windows, doors and skylights and to offer consumers an easy way of identifying energy-efficient windows. To participate in the program, window manufacturers sign a memorandum of understanding with the DOE. All windows must be rated, certified and labeled for both U-factor and SHGC by the NFRC.

According to the DOE, an average household spends more than 40 percent of its annual energy budget on heating and cooling costs. "If all new residential windows purchased in the United States over the next 15 years were ENERGY STAR models, $7 billion in energy costs would be saved," said Bill Noel, program manager for ENERGY STAR Windows.

Taylor said ENERGY STAR is a great way for consumers to determine what products are energy efficient. "Ten to 12 years ago, two different companies would be claiming the same performance but they would be 100 percent different from one another."

Taylor said consumers should follow the following steps when choosing a window:

1. Look for the "star."

2. Look for the NFRC label.

"Looking at it from a broad scope, I would say an ENERGY STAR window is 30 percent more efficient than the average window," said Curtis. "If the consumer knows nothing, they are better off purchasing an ENERGY STAR window because it performs better than 60 percent of window products."

According to Noel, many in the industry see the benefits of the ENERGY STAR program. Noel said Home Depot recently signed a memorandum of understanding to promote ENERGY STAR on a national basis because they saw how powerful the program was in California stores. "Home Depot is helping sell more energy-efficient windows," said Noel.

Criticisms of the ENERGY STAR Windows Program

While Taylor said all you have to do is look for the ENERGY STAR label, others disagree. "I don’t think it [ENERGY STAR] is an accurate predictor because many products exceed ENERGY STAR standards," said Kenney.

A positive aspect of the program is that ENERGY STAR goes a step further than NFRC by dividing the country into geographical regions based on energy costs for heating and cooling. While the program is praised for recognizing that different factors must be taken into consideration in different regions of the country, there are criticisms of the criteria set for these regional groupings. Following are the criteria:

Windows and doors must have a U-factor rating of 0.35 or below.

Windows and doors must have a U-factor rating of 0.40 or below and a SHGC of 0.55 or below.

Windows, doors and skylights must have a U-factor rating of 0.75 or below and a SHGC of 0.40 or below.

Marc Massa, sales manager, specialty products for AFG Industries in Kingsport, TN, is one of the manufacturers who questions why SHGC is not required in the North saying, "The credibility of the rating system is suspect." "All I agree with concerning ENERGY STAR is that the DOE made the first step to identifying different regions. There is a long way to go . . . but over time this could be a good program."

According to Noel, a working group was formed in July 1998 in response to issues brought forth by glass manufacturers. Noel said the DOE is evaluating the concerns raised by those in the working group, such as criticisms of the regional groupings and the absence of SHGC in the North. "When DOE launched the program we agreed to work with the industry to respond to compelling arguments to change the program," he said.

Noel said the industry is still faced with the problem of determining how to credit solar heat gain. "This problem was around way before ENERGY STAR," said Noel. "We didn’t have an industry consensus on how to credit SHGC."

Curtis disagrees. "I think they have done a good job considering all the factions involved," he said. "U-value is important in the North and SHGC is important in the South."

The fail to recognize the energy benefit of passive solar heat gain is another criticism of the program. "While the ENERGY STAR Windows program stipulates certain product performance parameters to qualify as ENERGY STAR compliant, the specific performance parameters do not currently recognize the benefit of passive solar heat gain in heating-dominated climate areas," said Gore. "The passive solar heat gain benefit is justified technically and we are hopeful that the program can be revised to include this aspect."

Doubling Use of Efficient Windows

According to Darius Arasteh, staff scientist for Lawrence Berkeley National Laboratories (LBL) in Berkeley, CA, approximately 35 percent of windows on the residential window market today are energy efficient. To increase this number, the Efficient Windows Collaborative (EWC) was formed with the goal of doubling current market share by 2005 (EWC is managed by the Alliance to Save Energy, based in Washington, DC). The ENERGY STAR program has a similar goal. "Our goal is to increase market penetration of energy-efficient windows to double what it is now," said Noel. He believes this is an achievable goal in the next five to seven years.

The EWC originally received funding in 1997 and spent several months signing up charter members including manufacturers and suppliers. This ended in 1997 when the EWC began enlisting regular members. According to Alecia Ward, EWC program manager, charter members agreed to label 90 percent of their products with NFRC by the end of 1998. Regular members agreed to label 50 percent of their products with NFRC by the end of 1999.

Ward continues to believe the EWC’s goal of doubling market share is a realistic one due to the targeting of efforts in areas such as Florida, Texas and California. "We are targeting regions where efficient windows would have a huge impact and significantly affect market share," she said.

The EWC is not only targeting large window manufacturers but is also trying to get regional manufacturers involved in the promotion of energy-efficient windows. "We recently had an influx of small manufacturers who signed on with us in the Northeast," said Ward.

Educating Builders and Consumers

Although Ward said the EWC targets a variety of groups such as window manufacturers, realtors, utility companies and remodelers, much of its efforts are targeted toward consumers and builders. EWC offers builders and other groups, sales materials and training. Ward says consumers look to builders for information, but in many cases builders are not well-informed of the benefits of energy-efficient windows. If builders are knowledgeable, it is only with the bottom line, said Ward. "You’ve got to hit builders on profit," she said.

Massa explained it is difficult for builders to promote energy-efficient windows because they build on a budget. For this reason, he said a higher percentage of low-E windows are in luxury homes. "The builder wants to put in aesthetically-pleasing windows at the least cost to him," said Massa. "Some energy- efficient windows are too expensive."

On the consumer side, Ward said many consumers do take the time to conduct research before purchasing a window. The EWC website receives 2,000 hits per month which tracks how deep people delve into the site. "If people are spending all of this money, they will spend the time to research it," she said.

Although some consumers are performing research, "most people aren’t that well-informed," said Roy Drake, director of float operations for Visteon Automotive Systems in Dearborn, MI. Others in the industry believe this as well. According to Arasteh, consumers and builders are driven by cost. "People don’t walk into a home and ask, ‘What kind of windows are here?’" he said. He added that builders are more apt to add something to the home like a Jacuzzi, where there is a perceived value for the consumer. "The consumer demand for efficient windows, just isn’t there," he said.

Others in the industry agree. "I’m not sure builders, let alone consumers understand what the various energy-efficient options mean," said Drake. He added that consumers spend their money on things that provide the most value to them. "If customers don’t understand the value of energy- efficient windows, they won’t pay for them," he said. "They know with fancy light fixtures, it has an intrinsic value."

"The consumer is becoming more knowledgeable about these [energy-efficient products]," said Gore. "Still, the average consumer doesn’t have an understanding of how a window performs."

According to Kenney, many people promoting or selling windows do not have enough technical knowledge to pass the message on to the consumer. "Windows are sold through a multitude of channels," he said. "Some do a very efficient job. With others, the chain is broken in a number of places and the message gets muddied and blurred."

But as consumer education efforts continue, some industry experts say these efforts will, in the long-term, lead to an increased awareness of the energy properties of glass in general and windows in particular. "Customers won't walk in and say, ‘I'd like a specific level of energy efficiency in a window,'" said Singel, "but they will be prompted to ask questions about energy efficiency when they walk in a retail environment and see a display for ENERGY STAR Windows, for example. This is a long-term objective of consumer education efforts."

Managers of glass and window retail shops will need to be better-educated about energy efficiency themselves. They can expect to be asked questions about U-values and other energy measures and could lose credibility if not informed.

Further Analyzing the Ratings

According to Massa, any appliance such as a refrigerator, dishwasher, etc., has a yellow label which displays the annual BTUs consumed. "Until we get to this point, the consumer won’t understand the benefits [of energy-efficient windows]," he said. "No consumer knows the meaning of U-factor or SHGC."

But according to Noel, consumers don’t need to understand these ratings. "The real purpose of ENERGY STAR is to take the effort away from the consumer," said Noel. They shouldn’t have to think about U-factor or SHGC."

Drake added that U-factor is very important, but certainly isn’t the only factor to be considered. "With all the products out there, performance factors are confusing. It is difficult to come up with a rating that takes the broad range of factors into consideration."

Drake gave the example of how a low SHGC might be good in Texas but may not be good in places such as Minnesota where there is a heating cycle.

"The ENERGY STAR and NFRC ratings are noble attempts to give the end consumer a reasonable way of choosing a window," said Drake. "But, I’m not sure they go far enough . . . but, with anything that’s always the conflict."

Changing the Ratings: Industry Efforts and Suggestions

So with all the criticism is anything being done to change the ratings? "Consumers say they need something simple and clear—more than ENERGY STAR," said Arasteh. LBL led the development of NFRC procedures and Arasteh chaired the U-value committee. He is now chairing the NFRC Annual Energy Rating Subcommittee. "We are trying to come up with a way to rate residential windows for national use to make them more consumer-friendly," he said.

Arasteh said he would like to see the committee develop something like a 0 to 100 or ten star schedule—similar to that found on a refrigerator.

However, the committee’s efforts started well before ENERGY STAR, about seven to eight years ago. "Then ENERGY STAR came along and developed a yes/no formula," said Arasteh. "We took a step back from development in the last year or two."

The committee will meet later this spring, but Arasteh said it is difficult to reach a consensus when those in attendance at meetings all represent diverse interests.

One of the issues where it is difficult for manufacturers to reach a consensus is solar gain. "We can’t come to a consensus on issues such as solar gain," said Singel. "While no one has abandoned hope, the issue is very complex . . .we’re not there today."

Annual Energy Consumption Rating

Massa feels strongly that there should be an annual energy consumption rating on a label. "A single annual energy rating would absolutely simplify the process," he said. Massa said there is even a software program currently on the market that could be used for this purpose. RESFEN calculates the heating and cooling energy use and associated costs as well as the peak heating and cooling demand for specific window products. It is one of many software programs developed by the DOE.

"Not only should the U-factor be measured, but the SHGC," said Massa. But, according to Massa, simply placing this information on a label is not enough. "There should be a correlation between the two."

Although Massa is a strong proponent of an annual energy consumption rating, no progress has been made yet. "Different people going in their own product directions makes it difficult for us to all agree," he said.

Industry Cooperation (or lack-of)

Douglas explained that it is very difficult to come to a consensus when you have competing interests in a room. "I am really proud of the way everyone has been able to come together," she said. But, some manufacturers don’t believe the industry has come far enough.

"Participants in the glass industry need to pull together on this issue," said Gore. "The total energy performance that a window contributes to occupant comfort in a home is very important to our industry and specifically to the selection of windows over other building materials."

Massa said part of the problem is the fact that glass manufacturers have differing ideas on how to change the ratings. "The problem with the inception of NFRC is that all glass manufacturers weren’t involved," said Massa. "This has now changed and all manufacturers are actively involved. Now getting something done is difficult because everyone wants their own way."

Curtis agreed saying the industry has "tried and failed" to come up with a consumer-friendly rating system, such as a miles-per-gallon system used with cars. "We’ve taken a very complicated science and tried to turn it into something very simple," he said. "We could not get together as an industry to simplify this."


The industry consensus seems to be correct. Purchasing an energy-efficient window is not as easy for the consumer as buying a home appliance such as a refrigerator or a dishwasher. But the question is, "Even if the standards and rating systems are changed, could it ever be this easy?" When consumers purchase household appliances do they need to take factors into consideration such as, what region of the country they are located, or what side of their home receives the most sun? Probably not.

"People want a simple answer," said Singel. But when asked if there is, or ever will be, a simple answer Singel replied. "I don’t think it is possible."

Although the industry may never achieve a "one-size-fits-all rating system," there are measures that may be taken to increase consumer knowledge, and that of others in the industry, thereby increasing the market share of efficient windows.

USGlass will continue to focus on energy efficiency in future issues, when we educate builders on the benefits of energy-efficient windows and how they may pass these on to the consumer. We will also discuss the DOE’s roadmapping initiative and congressional efforts to promote consumer tax cuts.

Tara Taffera is the editor of USGlass magazine.

Energy-Efficiency Innovative Programs & Products

News Bulletins

Energy Efficiency Warranty Program

A new energy warranty, the Certified Performance Home, is being tested in Colorado. The warranty guarantees a home’s energy usage as well as consistent indoor room to room comfort versus one room being consistently hotter or colder than another one in the house.

The program helps builders performance test their homes, offers verification of the testing for energy quality control and provides home buyers with a written warranty. CertainTeed Corporation, Valley Forge, PA, and E.I.C. of Lancaster, PA, created the program. In order to participate in the program builders had to meet predetermined performance and prescriptive standards validated through inspections and specific performance tests.

Once the standards are met, the homeowner is provided with a written warranty on comfort and heating/cooling energy usage. Homeowners are guaranteed that during the first year, comfort problems will be corrected at no charge. Heating and cooling usage is guaranteed for three years.

Technology Partnership Between GMIC and U.S. DOE

A voluntary agreement has been reached between the Glass Manufacturing Industry Council (GMIC–formed under the auspices of the American Ceramic Society) and the U.S. Department of Energy to identify, plan and perform research and develop technology demonstrations of mutual benefit to U.S. glass companies and the nation. The primary aim is to pursue pre-competitive research and development related to glass manufacturing that can improve energy efficiency and environmental quality, increase productivity and reduce emissions of greenhouse gases. The GMIC will represent the needs and interests of all sectors of the glass industry.

 FEMP Encourages Specification of NFRC-Rated Products

The U.S. Department of Energy’s Federal Energy Management Program (FEMP) has recommended that all federal government agencies specify products rated by the NFRC when purchasing windows for residential construction projects.

The new recommendation will affect such agencies as the U.S. Department of Defense and the U.S. Department of Housing and Urban Development, according to the NFRC. FEMP distributed a two-page fact sheet on How to Buy Energy-Efficient Residential Windows to all federal agencies in September.

At its fall policy meeting the NFRC also adopted NFRC 300, 1998 edition, a new procedure to verify the solar optical properties of glazing materials. The new procedure is said to improve the accuracy and reliability of all NFRC energy performance ratings. At the same meeting, the NFRC approved a new temporary door label intended to make it easier for door manufacturers to participate in the NFRC rating and labeling system.

 Energy-efficient Products

Comfort Ti from AFG

AFG Industries of Kingsport, TN, has introduced three options of its Comfort Ti low-emissivity residential glass that incorporates ultrahard titanium as a coating material.

The Comfort Ti-AC is a solar heat blocker designed for regions where air conditioning is used most of the year. Comfort Ti-PS provides high levels of passive solar transmission, capitalizing on the free energy resource to reduce heating costs in colder regions. The Comfort Ti-R is a balanced, high R-value product that provides superior energy efficiency throughout North America, according to the company.

Milgard Windows Offers SunCoat™

Milgard Windows, of Tacoma, WA, has introduced its high-performance glass, SunCoat. The glass offers improved solar performance and ultraviolet protection. The specially formulated low-E glass is particularly effective in sunny southern climates. The glass is designed to keep homes warm in the winter and cool in the summer. In cold temperatures, it helps trap radiant heat inside, and in hot temperatures it reduces solar heat gain. The glass also helps protect interiors from damaging ultraviolet rays, yet still lets in plenty of visible light, according to the company.

 Energy-efficient Promotional Tools

Andersen Windows Offers Energy Efficiency Promotional Kit

Andersen Windows Inc. of Bayport, MN, offers a promotional kit to help builders using their products market and sell energy-efficient homes. The kit comes in response to Andersen’s endorsement of the U.S. Environmental Protection Agency’s ENERGY STAR Homes Program. According to the company, the promotional kit, designed to educate customers about the economic advantages of purchasing ENERGY STAR-qualified homes, features Ernie G. Smartz, a cartoon character, and includes descriptive brochures and software.

 Alliance to Save Energy Releases Power$marts Brochure

The Alliance To Save Energy of Washington DC, offers a new booklet that demonstrates how energy-efficient technologies can cut utility bills by 30 percent, while also reducing energy use, air pollution and greenhouse emissions. The booklet focuses on ways energy may be saved in household uses by educating the consumer on the most energy-efficient appliances, light bulbs and electronics to purchase.

NFRC Publishes Certified Products Directory

The NFRC recently published its seventh annual Certified Products Directory. According to the NFRC, the directory provides consumers, builders, remodelers, architects, retailers, and others, with fair, accurate and reliable energy performance information. This includes U-factor, solar heat gain coefficient and visible transmittance ratings for nearly 40,000 windows, doors and skylights. 

Harmonization of U.S. and Canadian Window Standards

While the United States uses the National Fenestration Rating Council (NFRC) and the Department of Energy’s ENERGY STAR program as a way of gauging the performance of energy-efficient windows, these standards are measured differently in Canada.

In rating the performance of windows, the Canadian Standards Association’s (CSA) A440.2 standard, which generates the Energy Rating (ER) in the Canadian market, combines the energy impact of solar heat gain, U-value, and air infiltration into a single number, which provides a rating for net heat flow. A positive number means a window produces a net heat gain for a home’s interior while a negative number means the interior loses more heat than it gains through a window. To obtain a good ER, a window must have low heat loss, low air infiltration and high solar heat gain.

While the U.S. and Canadian standards differ, the American Architectural Manufacturers Association (AAMA), the Window and Door Manufacturers Association (WDMA) and the Canadian Window and Door Manufacturers Association (CWDMA) have been working to harmonize the two standards by developing the New North American Window Standard. The groups have been working together over a two-year time period in both the United States and Canada. The NFRC, the CSA, the National Research Council and the Institute for Research and Construction are also assisting in the effort.

According to Richard Lipman of the CWDMA, the harmonization effort is occurring in three different areas, with one of the sub-groups working on energy. A draft of the standard developed by the air, water and structural committee is currently out for public comment. According to Lipman, this group has accomplished a great deal which was the result of 23 days worth of meetings.

He admits that the energy efficiency group hasn’t been as productive yet and will meet again in early March. "The energy efficiency group is being reorganized and re- energized," said Lipman. "A lot of work has to be done but we anticipate the same things will happen with the energy efficiency group as it did with the air, water, structural group."

According to Lipman, the aim of the North American Window Standard is to provide a basis for product comparison for companies who do business in both the United States and Canada. "We want to get a fair basis to assist people in both countries to test and qualify their products," he said. —TT



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