Energy Efficient Windows Can Reduce Carbon Footprints…Oh, and Heating Costs, Too

Rich Walker
February 14, 2009
COLUMN : Industry Watch | Energy Efficiency

Although it's counterintuitive to think about global warming when a hard winter besieges the upper Midwest, we in the fenestration industry ignore the implications of global warming at our peril–at least in the sense that doing so will likely hamstring our businesses. The human role in global warming is heavily debated, but the political role is hardly questionable.

As a result, regulations, codes, tax credits and voluntary programs influence the marketplace and much of the consuming public and commercial buying influences are lining up on the safe side. Hence the deluge of green building initiatives and rating programs such as LEED or Energy Star. As noted in last month's column, McGraw-Hill Construction's Green Outlook 2009 report states that the value of green building construction starts was up five-fold from 2005 to 2008 and could triple by 2013.

To be sure, there is nothing wrong with saving energy and reducing product life cycle environmental stress, especially when taking into consideration the range of economically viable solutions with reasonable investment paybacks.

Consequently, we have grown accustomed to the tools of enhancing greenness – the efficiency with which buildings and their sites use and harvest energy, water and materials, and reduce building impacts on human health and the environment throughout the complete building life cycle. But as of late, another factor is gaining notoriety: the concept of the carbon footprint.

Shifting into Neutral
A carbon footprint is the sum of all emissions of carbon dioxide (CO2) induced–directly or indirectly–by an individual's, company's or industry's activities over the course of a year, typically expressed as equivalent tons of CO2. Driving a car releases a certain amount of CO2, depending on the fuel consumption and the driving distance. The production of food and consumer goods also emits CO2. When a building is heated with oil, gas or coal, CO2 is generated. Even if the building is heated (or cooled for that matter) with electricity, the generation of the electrical power by fossil fuels also emits CO2. What is important is not only the total amount of energy used, but also how the energy was produced in the first place (e.g. from fossil fuels or renewable resources).

The carbon footprint is also the amount of carbon dioxide (CO2) and other greenhouse gases emitted over the full life cycle of a product or service, including all possible causes that give rise to carbon emissions. All direct (on-site, internal) and indirect (off-site, external, embodied, upstream, downstream) emissions are taken into account. A complete life cycle assessment (LCA)–already a recognized "green" tool for assessing pollution contribution–is needed to accurately determine a product's overall carbon footprint.

The current theory is that carbon footprints are rendered smaller through the mechanism of carbon offsets, defined as balancing a project's or product's emissions with a design or alternative product that saves or stores an equivalent amount of CO2. Carbon offsets have also taken on financial value, in that a payment can be made to "buy" an offset–i.e., a dispensation to emit CO2 in exchange for contributing funds toward a project or technology used in offsetting the carbon emissions elsewhere. The most common project types are renewable energy, such as wind farms, biomass energy, hydroelectric dams, energy efficiency projects, the destruction of industrial pollutants or agricultural byproducts and destruction of landfill methane.

Such carbon offsetting has gained appeal and momentum as part of a trendy "carbon neutral" lifestyle among consumers who have become concerned about energy-intensive lifestyles and economies. A growing number of websites (, for one) feature interactive carbon counters that allow individuals and small businesses to calculate their approximate carbon footprint in terms of tons of CO2 emissions that they directly or indirectly contribute. The sites offer suggestions for carbon offset actions which often take the form of a suggested contribution toward some of those environmentally friendly projects.

Carbon offsetting could also become an official part of the "green" lexicon and rating schemes. It already has achieved a significant level of international legitimacy through certification systems and protocols that have been developed to register and trade carbon offsets. These systems use different methodologies for measuring and verifying emissions reductions, depending on project type, size and location, and act as a clearinghouse for trading monetarily valued offsets.

For example, the Chicago Climate Exchange (CCX) is North America's only voluntary, legally binding greenhouse gas (GHG) reduction and trading system for emission sources and offset projects in North America and Brazil. CCX employs independent verification, includes six greenhouse gases and has been trading greenhouse gas emission allowances since 2003. The 350 diverse members of the exchange–which includes corporations such as DuPont, Amtrak and Motorola, municipalities such as Oakland and Chicago, educational institutions and farm organizations–have committed to reducing their aggregate emissions by 6 percent by 2010.

According to the World Bank, in its 2007 report, State and Trends of the Carbon Market, about $5.5 billion of carbon offsets were purchased in the worldwide compliance market in 2006 representing about 1.6 billion metric tons of CO2 reductions. This is becoming serious business.  But, what does this mean to window manufacturers?

How Does This Affect You?
Frankly, all of this is nothing new in the sense that energy efficiency is a cornerstone of conservation, green design and carbon neutrality. Our industry has been working to reduce heat loss through windows, doors and skylights for more than 30 years, dating to the onset of the first "energy crisis." AAMA 1503, Voluntary Test Method for Thermal Transmittance and Condensation Resistance of Windows, Doors and Glazed Wall Sections, initially published in 1980, was the first attempt to establish a uniform and repeatable thermal performance testing protocol.

Window energy performance standards have since been developed by AAMA and by the National Fenestration Rating Council. NFRC ratings, recognized by the Energy Star Windows program, are the principal means of assessing residential windows for U-factor and solar heat gain performance. AAMA 1503 tends to be favored in the commercial and architectural sectors as the preferred means for verifying project-specific designs rather than mass-produced product lines.

Through these energy efficiency initiatives and aggressive R&D, we have solid credentials to participate in the goals of carbon neutrality, and we should be prepared to promote them:

  • Alternatives to drive down the U-factor have moved well beyond simple two-lite glass with a "dead air" space between. Inert gas (e.g., argon) infills, low-e and reflective metallic coatings that reflect heat inward or outward have vastly improved performance.
  • Warm-edge technology for insulating glass reduces heat transfer around the edges of insulating glass units. Traditional metal spacers conduct heat, causing the edges of the glass to lose more heat than the center, while warm-edge spacers use insulating materials (e.g., PVC foam) to increase the inside edge temperature by 10°F or more under the same conditions.
  • New framing materials have greatly improved inherent thermal performance, while new thermal barrier materials have greatly enhanced the thermal performance of traditional metal framing material.
  • Energy-robbing air infiltration rates have decreased, thanks to a variety of weatherstripping options for sealing the contact area between the fixed and movable sections of the window.

While we may not be to the point of trading carbon offsets on the open market, advanced window materials technology, design capabilities, standards, testing protocols and installation requirements position us well to move with the times, whether they're characterized by rating systems, greenness or carbon neutral lifestyles.

Keeping Up with the Latest Trends … and an Old One
Because the carbon neutrality trend is growing, it might be an interesting marketing project to develop our own "carbon footprint offset calculator" to show how replacing old windows with Energy Star-rated products in the different climate zones reduces CO2 emissions, based on different heating system fuels and cooling energy load. Another interesting project might be to assess the life cycle carbon footprint of the various fenestration product materials. If we don't do these, you can bet someone will sooner or later do it for us, and they might not be wholly unbiased.

Still, practicality must remain the watchword. Keep in mind that good old enlightened self-interest remains the principal reason to toot our energy efficiency horn. From the consumer's viewpoint, that means the impact on their checkbooks from reduced heating and cooling bills that can be leveraged into economic justification for newer technologies and efficiency features. Despite all the hype, this remains the primary reason that most consumers buy energy efficient windows–instead of the secondary benefits of greenness or carbon neutrality.

Rich Walker is president and CEO of the American Architectural Manufacturers Association, 847/303-5664,