Fenestration Product Framing Material Differences in Relation to Green Building
– Use of PVC as a Window Framing Material
The different green building authorities each approach fenestration material selection and use in slightly different ways but are all generally performance-based and encourage the use of life cycle analysis to determine environmental impact of any given material or product over its entire life span. A life cycle assessment endeavors to quantify and characterize all of the resource and pollution flows (inputs and outputs) associated with a particular material over its entire life cycle: from the harvesting or extraction of raw materials, through manufacture, installation, use, and reuse or disposal. The actual inputs and outputs are quantified in a life cycle inventory. They are then characterized according to their estimated contribution to environmental and health impacts. (Life cycle analysis definition from USGBC report cited below*)
USGBC is officially neutral on the use of PVC and is preparing to release a report that has been prepared by its Technical and Scientific Advisory Committee entitled "Assessment of Technical Basis for a PVC-Related Materials Credit in LEED®*. In this report, the group draws the conclusions that a scientific basis does not exist to support the de-selection of or any penalty for use of PVC and that "within product categories more and less desirable materials can be identified.” (page 11, pp. 7-8).
Further, specific to use as a fenestration framing material, the group reports that:
"The results for windows are remarkably similar across the product alternatives. This is because the total life cycle results are not dominated by the frame material, but rather by the glazing and the usage phase energy use.” (page 8, pp.32-34) and "Aggregated health impacts of carcinogens as well as particulate emissions show that the comparative performance of the window alternatives is entirely driven by differences in the energy efficiency of the studied alternatives. Thus, among our three frame types studied, the aluminum-framed window had the worst energy efficiency, while the wood and PVC-framed windows were virtually identical in efficiency. The proper conclusion to be drawn from this analysis is that from a life cycle human health perspective, the key issue is window energy efficiency rather than frame material.” (page 8, pp. 37-43)
USGBC’s LEED® Homes, LEED for Homes is a voluntary rating system that promotes the design and construction of high performance "green" homes. USGBC began the pilot test of LEED for Homes in August 2005. As of May 2007, about 375 builders representing 6,000 homes across the U.S. are participating in the pilot program, and over 200 homes have been LEED certified. The LEED for Homes pilot rating system has been in pilot phase for over a year and a half. After project feedback, internal review, and approval by LEED Technical Advisory Committees, the rating system was open for public comment. The LEED for Homes Public Comment is open until midnight, July 14th, 2007.
Likewise, NAHB’s Model Green Home Building Guidelines which are being adopted locally and are being promoted by the Green Building Initiative are material neutral, performance-based and encourage the use of energy efficiency as a material selection criterion. These guidelines also promote the use of materials that require no additional finish resources to complete application onsite (sec. 2.1.5).
Green Globes™, a competing green building program for commercial construction, is also material neutral, performance based and specifies the mandatory use of Energy Star for Windows (secs. 4.1-4.3)