A consensus process similar to what drives ASTM C 94 and ACI 318 is on track to deliver in 2009 an International Building Code-suited green building standard that recognizes structural materials’ recycled content
DON MARSH, EDITOR
A consensus process similar to what drives ASTM C 94 and ACI 318 is on track to deliver in 2009 an International Building Code-suited green building standard that recognizes structural materials’ recycled content. The American Society of Heating, Refrigerating and Air-Conditioning Engineers’ Standard For High-Performance Green Buildings Except Low-Rise Residential Buildings, or ASHRAE SPC 189.1, has code-adoption potential thanks to a format typical of IBC appendix documents. It would provide prescriptive guidelines as an alternative to the flexible LEED (Leadership in Energy & Environmental Design) rating point system.
The proposed standard, which ASHRAE is developing jointly with the LEED-administering U.S. Green Building Council and Illuminating Engineering Society of North America, is intended to provide minimum requirements for high-performance green building. SPC 189.1 addresses temperature control, ventilation and lighting, along with structural materials’ recycled content. In a concrete mix design, for example, it acknowledges the prospective recycling factor of supplementary cementitious materials.
Critics contend that structural materials are outside the scope and expertise of all three drafting agencies. The American Institute of Steel Construction (AISC) suggests the current SPC 189.1 draft shows an apparent lack of balance and expertise [that] has resulted in provisions AISC believes to be significantly slanted toward cement and concrete industry interests under the guise of encouraging less sustainable industries to become more sustainable.
AISC criticizes SPC 189.1 methodologies and cost calculations that result in a maximum 5 percent total recycled content credited to any one material specified on a project, noting: A typical structural steel frame provides an 11 percent credit toward the overall recycled content of a building. A concrete frame may provide one to two percent. At the same time, the reinforcing steel in the concrete structure will provide an additional 5 percent credit. The result: structural steel gets capped at 5 percent, while concrete gets its full credit and the 5 percent credit for rebar.
The Institute indicates a 90 percent recycled content factor for wide flange structural steel, and a 96 percent recycling/reuse rate for structural steel members removed from existing buildings. It also cites the limited possibilities for recycled content in concrete formulated for a building, including a (virgin-aggregate) mix where fly ash substitutes 25 percent of portland cement. Despite the fly ash representing perhaps 3 percent of a finished slab or structural member, the proposed SPC 189.1 would apparently allow a building designer to designate the concrete as bearing 25 percent recycled content.
This challenges the SPC 189.1P Committee to consider business on one hand and engineering on the other: 1) ASTM-grade structural steel Û the only kind allowable in a typical code-bound building Û can be milled with 90 percent recycled content; and, 2) Recycled-concrete aggregate would be limited or not allowed in ASTM-grade mixes specified for an ACI 318-compliant project.
Although not responding directly to AISC’s comments, Martha VanGeem, principal engineer of Portland Cement Association R&D subsidiary CTLGroup and a consultant on the ASHRAE SPC 189.1 standard, notes, Every paragraph of this document is controversial to some group. Each revision is a bump up for somebody, whether it be steel, wood, the glazing industry, and concrete. They are all unhappy with parts; it’s a pretty progressive standard.
SPC 189.1 is progressing toward a potential final draft, appropriately raising questions on the economics and limits of construction materials recycling.