LEED Guidelines and Fenestration Design
Not every building is designed to achieve LEED certification, but using the guidelines in the LEED Rating System can help lower utility costs, minimize the impact on our environment and improve occupant comfort levels. In this two-part blog, we’ll take a look at how “smart” fenestration designs and applications can significantly improve a building’s performance. Part one focuses on Energy & Atmosphere, Materials & Resources and Indoor Environmental Quality.
Energy & Atmosphere Credit 1: Optimize Energy Performance
Intent: To achieve increasing levels of energy performance to reduce environmental and economic impacts associated with excessive energy use.
• Design the building envelope and systems to maximize energy performance. Utilize aluminum and glass manufacturers’ most energy-efficient products.
• Determine required minimum total system U-Factor based on aluminum framing system and glass type. Reference National Fenestration Rating Council (NFRC) 100-2010: “Procedure for Determining Fenestration Product U-Factors.”
• Determine required maximum Solar Heat Gain Coefficient (SHGC). Reference NFRC 200-2010: “Procedure for Determining Fenestration Product Solar Heat Gain Coefficient and Visible Transmittance at Normal Incidence.”
Recent improvements in thermal break technology have helped aluminum glazing systems become more energy efficient due to conductive heat loss. The graphics below show a true thermally broken curtainwall, thermally broken entrance with frame and a fiberglass pressure plate for conventional curtainwall. The fiberglass provides a significant improvement over the more common aluminum pressure plate (see image below).
Energy and Atmosphere Credit 2: On-Site Renewable Energy
Intent: To encourage and recognize increasing levels of on-site renewable energy self-supply to reduce environmental and economic impacts associated with fossil fuel energy use.
Consider integrating photovoltaic (PV) panels as part of the storefront and/or curtainwall glazing systems. Where natural daylight is desired, some PV panel manufacturers offer semi-transparent building integrated photovoltaic (BIPV) modules that can generate electricity and transmit light.
The Tiger Woods Learning Center incorporated a 21-by-65-foot curtainwall system by Wausau Window and Wall Systems utilizing photovoltaic modules from SCHOTT North America Inc. The lites varied in opacity and power-generation: The top panels of the PV array produce 72 watts each with an opacity of 5 percent, while the lower panels offer 25 percent opacity and produce 60 watts of energy. The BIPV system can produce 3,800 kilowatts of energy per year (see image below).
Materials and Resources Credit 4: Recycled Content
Intent: To increase demand for building products that incorporate recycled content materials, thereby reducing impacts resulting from extraction and processing of virgin materials. This credit requires the total recycled content of the building based on cost be 10 percent for one point or 20 percnet for two points.
• Use materials with recycled content such that the sum of postconsumer recycled content plus half of the pre-consumer content constitutes at least 10 percent or 20 percent of the total value of the materials in the project.
• Identify aluminum framing manufacturers that provide significant recycled aluminum content in their systems.
Aluminum requires significant amounts of energy to convert bauxite to the finished goods. The “Embodied Energy” in prime aluminum is more than 100,000 BTUs per pound. However, it only takes 1/5 of that energy to process recycled aluminum. By recycling aluminum, we recover the energy that was used in converting bauxite to aluminum in the smelting process.
Indoor Environmental Quality Credit 4.1: Low-Emitting Materials – Adhesives and Sealants
Intent: To reduce the quantity of indoor air contaminants that is odorous, irritating and/or harmful to the comfort and wellbeing of installers and occupants. All adhesives and sealants used on the interior of the building (i.e., inside of the weatherproofing system and applied on-site) must comply with the following requirements as applicable to the project scope.
• Specify low volatile organic compound (low-VOC) materials in construction documents. Ensure that VOC limits are clearly stated in each section of the specifications where adhesives and sealants are addressed.
• Adhesives, sealants and sealant primers must comply with South Coast Air Quality Management District (SCAQMD) Rule #1168. VOC limits listed in the table below need to be adhered to for storefront and curtainwall installations:
Application/VOC Limit (grams/liter less water)
Structural Glazing Adhesives: 100
Architectural Sealants: 250
Sealant Primers, nonporous: 250
Sealant Primers, porous: 775
Indoor Environmental Quality Credit 4.2: Low-Emitting Materials—Paints and Coatings
Intent: To reduce the quantity of indoor air contaminants that is odorous, irritating and/or harmful to the comfort and wellbeing of installers and occupants.
• For projects that require on-site painting or repair of a buildings interior, specify low-VOC paints and coatings in construction documents. Ensure that VOC limits are clearly stated in each section of the specifications where paints and coatings are addressed.
• Track the VOC content of all interior paints and coatings during construction.
Note: With the exception of possible field repair of finishes, this requirement does not pertain to architectural aluminum anodizing or paint. All finishes are applied off-site and will not contribute to contaminants in the building.
Kynar® paint has been the proven mainstay in the architectural market for decades. The primary environmental concern with liquid paints is the solvents used to deliver the paint to the part; some of the solvents used are considered VOC content and must be destroyed. Environmentally conscious finishers, such as Linetec, which provided the photo below, use a 100 percent air capture system and destroy the VOCs with a regenerative thermal oxidizer, so there is no adverse environmental impact (see image below).
Next month’s blog will continue with LEED credit categories 5, 6 and 8.