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Proposed ASHRAE Standard Delves into Structural Issues
Posted by Geoff Weisenberger on May 22, 2008 at 10:15 AM.

The structural steel industry has a long track record of success in sustainable development, consistently leading the way in implementing energy, carbon, and resource utilization improvements for the past 25 years. Today, however, the structural steel industry is faced with a significant challenge, one that originates not from a lack of accomplishment with respect to sustainability, but rather from being too successful in this area.


AISC has significant concerns with some provisions in the recently published second draft of the proposed ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) Standard 189.1, Standard for the Design of High-Performance Green Buildings Except Low-Rise Residential Buildings. AISC’s concerns with this proposed standard are that:


  1. It is outside the scope and expertise for which ASHRAE is ANSI-accredited.
  2. It will result in adverse environmental impacts.
  3. It includes provisions that are unfair to steel, and inappropriately preferential to the interests of the concrete industry.
  4. It adversely restricts the freedom of design professionals in their selection of structural framing materials.


The proposed ASHRAE standard being developed jointly with the U.S. Green Building Council and the Illuminating Engineering Society of North America is intended to provide minimum requirements for high-performance green buildings.


While addressing HVAC and lighting issues, the standard also establishes prescriptive requirements for construction materials, an area that AISC believes to be outside the scope and expertise of ASHRAE, USGBC, and IESNA. In addition, the committee responsible for the proposed 189.1 standard was not constituted in a balanced manner under appropriate ANSI consensus protocol. AISC also believes that the committee lacks expertise in the area of construction materials, particularly as they relate to structural framing systems.


This apparent lack of balance and expertise has resulted in provisions that appear to be significantly slanted toward the interests of the cement/concrete industry under the guise of encouraging less sustainable industries to become more sustainable.


For example, today a typical structural steel frame provides an 11% credit towards 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% credit. The proposed standard will limit the contribution for any material at 5%. The result: structural steel gets capped at 5%, while concrete still gets its full credit AND the 5% credit for reinforcing steel.


Similarly, the definition of recycled content is that portion of a material by mass that originates in either pre- or post-consumer waste streams. But the ASHRAE committee has decided to allow the calculation of the recycled content of concrete to violate that definition. Instead of reflecting the actual recycled content of the concrete, ASHRAE 189.1 allows the recycled content of the cementitious portion of the concrete to be used as the recycled content of the entire concrete mix.


For example, at present, substituting 25% fly ash for Portland cement in concrete with no other recycled content, results in an actual recycled content of 3%. Under ASHRAE 189.1 the cement and concrete industries are allowed to claim a 25% recycled content.


The committee’s justification is that they wish to encourage the use of fly ash in concrete. In reality, they are discouraging the use of recycled aggregates, removing over 50% of the mass of a concrete building from green considerations and providing the cement/concrete industry with an unfair advantage in the marketplace.


It is not the role of a standard to provide incentives and to favor particular products. The selection of structural framing materials should be based on the merits of the materials as judged against a consistent metric.


The inclusion of this standard in building codes is being encouraged by ASHRAE as an appendix at the national level available for local adoption. Including these provisions in a local building code will significantly limit the opportunity of design professionals to select construction materials for high-performance green buildings that properly balance economic, environmental, and design issues.


The structural steel industry believes strongly in the need for high-performance green buildings. AISC also believes that standards for the selection and optimization of structural framing materials should be developed in a balanced, consensus-based ANSI process that engages design professionals, industry associations, and interested parties with the required level of expertise to develop a fair and environmentally sound standard. AISC would welcome the participation of the concrete, cement, masonry, wood, precast, light-gauge steel, per-engineered building, and any other affected industries in that process.


AISC’s objection to 189.1 is not a rejection of sustainable construction practices or the need for green buildings. Much to the contrary, AISC’s commitment is to continue to be the leader in sustainable construction materials and to actively pursue additional sustainable practices within our industry.


When the domestic structural steel industry experienced a rebirth 25 years ago, purposeful decisions were made to create a sustainable industry. A central decision was the transition from basic oxygen furnaces (using iron ore and coke) to electric arc furnaces (using scrap as the primary raw material and electricity and natural gas as energy sources).


The gains from this transition have positively impacted sustainable construction:


  • Wide-flange structural steel products average in excess of 90% recycled content.
  • A 96% recycling/reuse rate for structural steel members removed from existing structures.
  • An increase in mill productivity by a factor of 20 moving from 10 to 12 man-hours per ton to 0.6 man-hours per ton.
  • A reduction in energy consumption per ton of product by 30%.
  • A reduction in carbon emissions by 47% since 1990; by comparison, the Kyoto protocol would have mandated a 5.2% reduction by 2012.
  • A recycling rate for automobiles now exceeding 100%, emptying out salvage yards.
  • The elimination of all production water discharges and the minimization of water utilization.
  • An increase in the strength of structural steel by 38% over the past 10 years, reducing the quantity of structural steel required in a typical building.


For more information, contact Scott Melnick, AISC’s vice president of communications, at


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