Volume 19,  Issue 1                                                   Spring 2005

Easy Being Green
Glass Usage Offers Opportunities for Sustainable Building Design

The dictionary definition of “green” has changed to reflect a growing interest in environmental preservation.

To be green is to be pro-environment and to have a desire to sustain the environment for future generations. Sustainable design and construction is based on protecting natural resources, saving energy and reducing the impact of buildings on human health and the environment over the life span of the building.

The architectural glass community has an important role to play in the design and performance of green buildings. 

According to Greg Carney, technical director of the Glass Association of North America, architectural glass plays a critical role in the design of sustainable buildings. 

“From the exterior building envelope to interior finishes and partitions, today’s architectural glass products provide design professionals tools to achieve transparency and thermal comfort while moving natural daylight further into the building,” says Carney. “We’re also seeing an increased use of glass in interior walls and partitions, and with mirrors in order to provide the comfort of natural daylight to those in the inner core of their buildings.”

Emerging Concerns for the Energy 
In 1973, Americans faced the OPEC oil embargo, started thinking about their dependency on fossil fuels. As a result of the energy crisis the Department of Energy was established in Washington, D.C., to address energy usage and conservation. The Solar Energy Research Institute (now called the National Renewable Energy Laboratory) in Golden, Colo., began investigating energy technologies. The glass industry began to promote the value of insulating glass units to minimize heat loss through windows and doors. Reflective coatings on glass followed, especially in warm areas of the country, to minimize solar heat gain into the building. 

Sustainability in buildings soon emerged as a key issue for architects. The turning point for the green building movement came in 1993 when the American Institute of Architects (AIA) joined forces with the International Union of Architects to sign a Declaration of Interdependence for a Sustainable Future. Then-president Bill Clinton even jumped on the green bandwagon that year when he offered up the White House for an energy audit that ultimately produced annual energy and water savings of $300,000. 

United States Green Building Council
At the center of the green building movement is the United States Green Building Council (USGBC). Formed in 1993, its primary goal was to create a sustainability rating system for buildings. The LEED—Leadership in Energy and Environmental Design—green rating program was the result. Buildings that are designed to LEED standards follow a point-based system that results in different levels of certification. There are five categories in the LEED program relating to the following: the site of the project; water conservation; energy; materials; and indoor environmental quality. There is also an innovation and design category. Daylight-ing is just one important part of green building projects, and creates a significant opportunity for the use of glass products.

Opportunities for green building design are growing as the LEED program expands into both the commercial and government construction sectors. Some government agencies have incorporated LEED requirements into their construction specifications or are requiring LEED certification. The General Services Administration (GSA), for example, requires all new GSA construction to seek LEED Silver status. 

But adoption of LEED is not restricted to the federal government. Cities, counties and whole states are looking to LEED for guidance in new construction. California, for example, offers Savings by Design, an incentive program for building owners who invest in energy-efficient designs. New York State is offering a green building tax credit for commercial and multi-family buildings that meet green standards. 

The program is also part of the curriculum at many colleges and universities. Private companies are asking for LEED certification as they embark on new building projects. Architects are looking for durable buildings that utilize cost-competitive products that are manufactured within close proximity to the building site. The use of renewal resources, ability of products to be recycled, the recycled content and the recyclability of packaging are other prominent concerns.

Opportunities for the Glass Industry
Energy-conserving glass and window products that comply or exceed the requirements contained in ASHRAE Standard 90.1 enable architects to control conductive heat loss or gain, solar gain from direct radiation and lighting in commercial building projects. “Energy-conserving glass products and the fenestration systems that use these value-added products provide a huge opportunity for architects to address the country’s commitment to reducing energy demand,” says C.R. (Carl) Wagus, technical director for the American Architectural Manufacturers Association. “More glazing can be used to provide natural daylighting and increased exterior visibility for occupants while still maintaining a favorable energy budget.” 

The glass industry offers a variety of energy-conserving projects, including low-E coatings that reduce long-wave radiative heat transfer, spectrally selective tinted or coated glasses that reduce solar infrared radiation and allow visible light transmission, low-conductivity gas fillings that reduce thermal conductance between glass layers, low-conductivity warm-edge spacers that help eliminate edge-of-glass thermal conduction effects caused by metal spacers and enhanced window designs with thermal barriers that reduce conductive heat loss.

These products enable architects to expand their use of glass in new ways that maximize daylighting benefits. According to Scott Hoover, senior manager-architectural marketing, Pilkington North America, “Architects continue to utilize more daylighting in their designs as it reduces electricity use as well as improves occupant comfort. The glass industry offers numerous products that enhance daylighting while still addressing other considerations such as glare control and façade uniformity.” 

Since artificial lighting is the single largest energy end use in commercial buildings, LEED building projects seek to incorporate daylighting strategies to save electric lighting energy, thereby reducing HVAC loads. In addition, daylighting offers increased comfort and satisfaction for building users. According to studies conducted by the Heschong Mahone Group, the use of daylighting can stimulate retail sales, increase worker productivity, and improve student test scores. 

Green building design may incorporate clerestories, skylights, light shelves, louvers, window shades and innovative glazing systems. While upper parts of windows will be designed to have high visible transmittance to maximize daylighting, lower sections consider the need for glare reduction.

LEED rewards daylighting, along with occupant views in Indoor Environmental Quality a Credit 8. 

Glass Recycling
Flat glass producers recycle glass that has been discarded during the glass manufacturing process. Referred to as cullet, this glass is generated from the process itself. It may be broken glass or part of the unfinished float ribbon edges discarded after cutting. Cullet that is generated at a float plant is recycled into production. Due to extremely high and ever-increasing quality demands, float glass manufacturers cannot use mixed cullet sources. In the last five years, significant progress has been made in utilizing coated architectural glass as another source of cullet. 

The use of float glass as a recyclable building material, in and of itself, does not qualify for LEED points because the cullet from the manufacturing process has not been diverted from a landfill. According to Mike Turnbull, director of international environmental management at Guardian Industries, “The challenge for the industry is for large users and fabricators to partner with their float glass suppliers to return uncontaminated, high-quality recyclable cullet. The benefit of this type of arrangement is that it may qualify for LEED points as this source of cullet is being diverted from a landfill.” 

Window/architectural glass is not recycled into the flat glass process due to cost, logistics and the possibility of introducing contaminants into the batch. There are cases where art glass has been made from glass scrap, however, there are more opportunities for recycling glass into nontraditional markets, such as in road construction, fiber-glass and foam-glass insulation, ceramic tiles, wall finishes and decorative pavers. 

The green architecture movement is growing by leaps and bounds, and architectural glass can play a significant role. Glass products offer a natural choice to expand daylighting and save energy. Is this a passing interest? Many will agree, the green movement is here to stay.

1. White Paper on Sustainability, Building Design & Construction, November 2003. 
2. “Skylighting and retail sales,” Heschong Mahone Group, August 20, 1999.
3. “Using advanced office technology to increase productivity,” Rensselaer Center for Architectural Research, 1992.
4. “Daylighting in schools,” Heschong Mahone Group, August 20, 1999.
5. “The Role of Daylighting in Green Building Design,” Environmental Design+

Resource Guide
To learn more about green building design, visit these websites:
U.S. Green Building Council,
U.S. Department of Energy, Smart Communities Network,
Environmental Protection Agency,
Northeast Sustainable Energy Association,
G/Rated (Portland Office of Sustainable Development,
Green Building Services,

Valerie Block is a senior marking representative in DuPont’s Glass Laminating Solutions business, based in Wilmington, Del.

Architect's Guide to Glass & Metal
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