Saturday, September 29, 2012

Life Cycle Assessment Software Now Free Download

The Athena Impact Estimator® (IE) is the most widely used North American life-cycle assessment tool made for designers that allows one to choose the structural system and specification. In order to significantly increase the user base of the IE within the architectural/engineering design community, the software is now offered free of charge. Visit for more information and to download.

The SEI Sustainability Committee is recognized in Athena Institute’s recent press release for our contribution to improvements made to their latest version of the Impact Estimator® (Version 4.2.01, released Sept 2012).  The LCA working group of the committee issued a wish list to Athena in late 2011 and worked through the year to fulfill one of the top wish list items: the addition of composite floors (concrete-filled metal deck over steel beams) to the floor and roof assembly options. This effort took a bridging of Athena with AISC and ensuring the translation of data from AISC into the tool met the needs of structural engineering users. The LCA WG will continue to push for implementation of other wish list items in the next release.”
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Friday, September 21, 2012

Structure and Carbon: How Materials Affect the Climate


The following is excerpted from the Carbon Working Group's upcoming white paper:

The embodied impacts associated with building materials (including structural materials and other finishes and equipment) comprise a relatively small part of the total environmental impact over the life cycle of a structure, with impacts from heating and cooling typically far outweighing the materials impacts. In North America, the relative life-cycle carbon emissions due to building structural materials alone can range from 1 to 16 percent for a 50-year building life, depending upon the building type, energy efficiency, and location.

However, a study of demolition records found that over 60% of the demolished concrete buildings were less than 50 years old, and roughly 10% were less than 25 years old. The numbers were even more striking for the steel-framed buildings: more than 80% of these buildings were less than 50 years old when demolished, and 40% less than 25 years old. For these short-lived buildings, the embodied impacts of the structural system could easily exceed 1/3 of the total life-cycle building impacts for buildings that are highly energy efficient.

The green building movement has primarily focused on improving operating efficiencies to reduce carbon emissions, and building energy efficiency is likely to improve. As a result, the relative embodied impacts of building materials will likely grow. To decrease our risk of exposure to disastrous climate-related events, we must not only reduce emissions from building operations but also reduce embodied emissions in building materials including structural materials. The success of this task depends in large part upon structural engineers who understand the emissions associated with the materials they use and who can use data, design, and material research to reduce the carbon emissions associated with their projects.
So structural engineers are faced with both a challenge and an opportunity.  

Use this site to learn about structural design's contribution to climate change, and become part of the movement for solutions.
Tuesday, September 18, 2012

How to Reuse a Floating Bridge

Seattle's 520 Floating Bridge
The Washington State DOT has required that the design-build team for a new bridge must reuse or recycle the existing bridge in a sustainable way. An international design ideas competition has been born of this challenge. Favorite options for reusing the existing pontoons have included floating docks, breakwaters, and piers. It's likely that the winner of the ideas competition will be more creative.

Results of the competition are to be announced live at the 2012 Seattle Design Festival and subsequently posted online. Log on to view the winning design. Did you have a better idea? What other design options come to mind? Please share your comments here.
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Tuesday, September 11, 2012

Coal Waste Processors Sue EPA

Coal waste products, like flyash, have long been used as complimentary cementitious materials to improve strength and durability of concrete while reducing cement content and therefore the embodied carbon of concrete. Until recently, even the EPA has been supportive of the commercial use of such materials. Now the EPA is taking a second look at the heavy metal content in these byproducts. A final ruling on whether to classify these materials as hazardous waste remains in limbo, but the uncertainty has angered the largest coal waste producers who have filed suit against the EPA demanding a deadline for the ruling.

Jim Vallette of the Healthy Building Network has published an interesting article outlining the positions of each side on this case. Online at

This issue was addressed in a previous blog article on this website: House Bill Takes on EPA Ruling Process
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Friday, September 7, 2012

Thermal Bridging in Concrete


The thermal bridging group is progressing on their next publication through ASCE. One new point of focus in this publication is thermal bridging through other materials. One common building material that is often overlooked as a thermal bridge is concrete. 

Although concrete isn’t nearly as conductive as steel, where it acts as a bridge it can still cause substantial energy loss. One of the most common examples of this is at balconies. Often the balcony is merely a cantilever of the main floor slab. Because of this, there is no continuous envelope or insulation barrier. In high rise condos and apartments, these can almost be visualized as fins on a radiator, as they behave in much the same way. 

One way to avoid or reduce this bridge is with a proprietary break. These systems are designed to still transfer the cantilever forces (shear and moment), while reducing the bridging to isolated stainless steel bars. Although widely used in Europe, these systems are not commonly found in the states. The Thermal Bridging group will be looking at these cantilever concrete conditions more closely in the next publication.

Thermal Bridging Working Group update by web liaison Raquel Ranieri, P.E., LEED AP BD+C. Read more recent articles about thermal bridging here.
Tuesday, September 4, 2012

The Value of Structural Engineering to Sustainable Construction


Numerous rating schemes have been proposed to incentivize green design, but how well do these codes relate to the building structures. The Institution of Structural Engineers set out to identify which green codes, if any, successfully addressed structures. Their report, titled The Value of Structural Engineering to Sustainable Construction, takes a methodical look at provisions in eight main categories common to most of the rating systems:
  1. Reuse
  2. Reduction of Portland cement
  3. Recycled content
  4. Responsible sourcing 
  5. Local sourcing
  6. Life cycle assessment
  7. Efficiency & future proofing
  8. Health implications
The conclusions are generally predictable, but the report does a nice job of recommending changes to improve the codes. Highest on the list are needed changes to those credits witch promote a perversion of the sustainable intent, like achieving full recycled content credit by using structural steel (over 90% post-industrial recycled content by nature) or using more interior finish for it's recycled content when a polished concrete wall would be perfectly fine. The best features of the report are the meticulously researched figures and user surveys. Anyone preparing a talk on sustainable structures should read this report for statistical backup to their conclusions.

Download the report at:

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