Thursday, August 31, 2017

Carbon Group Post 4: Do you know how to achieve a carbon-efficient steel-framed building? Your fabricator does.

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A common misconception within the Architecture/Engineering/Construction community is that structural steel is a carbon-intense, “dirty” product which sabotages the natural environment by utilizing large amounts of mined content.  In reality, the steel structure being fabricated for your current project has a decent chance of containing metal from a car similar to the one you were driving when you were 16.  
Figure 1 - The structural steel life cycle Credit: American Institute of Steel Construction

Domestic structural steel and rebar are produced with an average of 90% recycled content.  The process in which they are produced transitioned in the late 1970s from the Basic Oxygen Furnace (BOF) process to the Electric Arc Furnace Process (EAF).  This shift resulted in a 24-fold increase in productivity - from 12 hours per ton of steel to one-half of an hour per ton.  Steel products are also transported efficiently in the US, with the majority of steel being transported via barge or rail rather than truck.

Some lighter gage material, like decking and light gage studs, as well as Hollow Structural Sections (HSS) are made via both EAF and BOF.  The BOF process utilizes approximately 30% recycled content.   It is important to be able to differentiate between production processes for all types of steel used on your project when accounting for the carbon impact.  (In this post, as well as the carbon working group white paper, the term “carbon” is used to mean “carbon-dioxide equivalent.”) Versions 2 and 3 of the LEED rating system assume a 25% recycled content for all steel products as a default unless documentation via mill-specific data is provided.  In LEED v4, mill-specific recycled content data can be used to achieve the Leadership Extraction Practices option of the Building Product Disclosure and Optimization credit. 

The cradle-to-gate Environmental Product Declarations (EPDs) released by the American Institute of Steel Construction (AISC) in 2016 for fabricated hot-rolled structural shapes, fabricated HSS, and fabricated plate material provide a full accounting of material sourcing, production, transportation to fabrication shop, and labor and processing in the shop. However, only fabricators who were members of the Institute when it was produced (or have since joined and submitted environmental data) are able to legally use these EPDs to account for carbon content on their structures.

The EPD for Fabricated Hot-Rolled Structural Sections gives results for the impact category of Global Warming Potential (GWP) as 1.16 tons CO2e per ton of steel produced, with approximately 85% of the total impact coming from the furnace production process.  With the material production impact being the dominant contributor to the total impacts, it is important to be sensitive to overall material use when lessening carbon impacts is the overall goal.  
Figure 2 - Comparison of structural steel frame in the Empire State building as constructed in 1931 vs. now.  Carbon emissions numbers include material production only.  Credit: American Institute of Steel Construction

Material, however, is only one side of the coin regarding overall sustainability.  An argument can be made that designing an erection-friendly structure can also lessen carbon impacts by reducing schedule and saving weeks of labor in the field, although this has yet to be quantified by an official EPD or Life Cycle Analysis (LCA).   

In order to find the “sweet spot” where material efficiency, up-front cost, life-cycle cost, and resiliency come together, one needs to discuss specific project goals with the structural steel fabricator as early as possible – preferably as a preconstruction partner.  The fabricator will be able to educate the design team on local material supply, desired connection schemes, how material can most efficiently run through their shop, as well as be efficiently sequenced in the field. They can aid in implementing green goals such as overall material reduction (both with a material efficient structure and by exposing structure to reduce finishes), material reuse, and integrated process credits. 

The Steel chapter of the upcoming White Paper “Structures and Carbon” describes and compares production processes used domestically.  Specific strategies to produce a carbon-efficient structure are presented.  We look forward to your reviews and comments!
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Thursday, July 20, 2017

Carbon Group Post 3: Example Demonstrating How SCMs Can Reduce Embodied Impacts of a Concrete Building

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This is the third in a planned series of blog posts on topics that are discussed in depth in the SEI Sustainability Committee’s forthcoming technical report, Building Structure and Global Climate, due out later this year.

In this example, a cradle-to-gate LCA was conducted to determine the embodied impacts of concrete on a building to compare the Global Warming Potential (GWP) of a reference building using typical concrete mixes with moderate amounts of Supplementary Cementitious Materials (SCMs) such as fly ash and slag and a proposed building using concrete mixes that have relatively high volumes of fly ash and slag. The building is an 18 story residential tower located in the northeast United States. Compressive strengths for each structural element are identified in Figure 1.




Figure 1. Specified compressive strength of concrete for an 18 story residential tower.

The first step in the analysis is to identify typical concrete mixes for the reference building. In 2014 (updated in 2016), National Ready Mixed Concrete Association (NRMCA) published benchmark mix designs and their environmental impacts for eight different regions in the United States (www.nrmca.org/sustainability). This example uses the benchmark mix designs for the Northeast region. 
The next step is to estimate mix designs that have significantly lower GWP than the benchmark mixes that still meet the performance criteria (strength, durability, etc.). This example uses high volume SCM mixes from the NRMCA Industry-Wide Environmental Product Declaration (EPD). A summary of the concretes selected for the reference and proposed building are provided in Tables 1 and 2.

Table 1. Mix designs selected for the reference building (from NRMCA benchmark report)

Concrete Element
Specified Compressive Strength (psi)
Portland Cement (lbs/yd3)
Slag
(lbs/yd3)
Fly Ash
(lbs/yd3)
SCM content
Mat Foundation
6000
782
119
82
20%
Basement Walls
5000
741
112
78
20%
Floors B2-1
5000
741
112
78
20%
Floors 2-18
5000
741
112
78
20%
Shear Walls
6000
782
119
82
20%
Columns
8000
967
147
102
20%

Table 2. Mix designs selected for the proposed building

Concrete Element
Specified Compressive Strength (psi)
Portland Cement (lbs/yd3)
Slag
(lbs/yd3)
Fly Ash
(lbs/yd3)
SCM Content
Mat Foundation
6000 psi
256
342
256
70%
Basement Walls
5000 psi
242
323
242
70%
Floors B2-1
5000 psi
512
0
341
40%
Floors 2-18
5000 psi
581
0
249
30%
Shear Walls
6000 psi
427
256
171
50%
Columns
8000 psi
503
302
201
50%

Using the Athena Impact Estimator for Buildings (Athena IE) software (www.athenasmi.org), the reference building and proposed building were defined using the proposed mixes in Table 1 and 2 respectively. Athena IE has the NRMCA benchmark mixes and the NRMCA Industry-Wide EPD mixes pre-loaded into the software. The software also permits the user to define new mixes based on the existing mixes in the library or completely new mixes if that information is available from a concrete producer.

Once all the concrete information is defined for each project, the user can then run a report that will provide the estimated GWP, along with other impacts, for each building. The reference building will represent the largest impacts and the proposed designs will represent lower impacts. The results for this example showed that the reference building has a GWP for concrete of 6.14 million kg CO2 while the proposed building has a GWP for concrete of 3.92 million kg CO2 meaning that the high volumes of fly ash and slag mixes resulted in 36% reduction in GWP as shown in Figure 2.



Figure 2. Summary of GWP for reference building and proposed building.


Keep in mind, this is example was simplified for illustration purposes. It only considered the effects of concrete during the material extraction and manufacturing stage on the environmental impacts of the building. The Athena IE software does contain environmental impact information for most materials and products used in buildings and allows input of operational energy data for conducting a more comprehensive whole building LCA.
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Thursday, June 15, 2017

Carbon Group Post 2: What About the Data?

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Carbon Group Post 2: What About the Data?

This is the second in a planned series of blog posts on topics that are discussed in depth in the SEI Sustainability Committee’s forthcoming technical report, Building Structure and Global Climate, due out later this year.

As with all analyses, the quality of environmental assessment results depends greatly on the quality of the input data. What we learned in our earliest structural engineering and computer programming courses holds true: garbage in = garbage out. When it comes to environmental analyses of our structures, no matter the level of detail of the analysis—carbon dioxide equivalent footprint (carbon footprint), life-cycle inventory, or life-cycle analysis (LCA)—quality input data is important to achieve credible, verifiable, and consistent results.

Uncertainty in analyses related to data quality and variability is important enough that an entire chapter of the SEI Sustainability Committee’s forthcoming technical report is devoted to the topic. In this post, I’ll highlight the key questions to ask related to data when evaluating a carbon footprint.

Data quality and variability
When performing a carbon footprint, data typically can be taken from a few different types of sources:
·         Public databases
·         Private databases
·         Primary data
A public database is usually managed by an association or a public or private institution. In the U.S., one public database is the U.S. LCI database and it is managed by NREL. Private databases can belong to large consulting firms that have performed multiple LCAs or software companies. Lastly, primary data can be obtained directly from product manufacturers. These data are the most applicable to the analysis, yet they are typically the most time consuming and expensive to get. In all cases, data for use in carbon footprint studies includes quantities of materials and energy that go into the system boundary being studied, and emissions to land, water, and air that come out of the system boundary.

Regardless of the source, data used in carbon footprints should be accompanied by evaluations of data quality and variability. Unfortunately, most LCI datasets do not include statistical variability. Information such as standard deviation and statistical distribution can be useful when evaluating or comparing carbon footprints. When evaluating an LCA report or EPD, research whether average data from public or private databases is representative of the industry. Keep relative uncertainty and statistical significance in mind when using data and results. Another way to check reliability of results is to request uncertainty/variability information from suppliers and trade organizations.

Data quality guidance is given in ISO standard 14044, Environmental Management-Life Cycle Assessment-Requirements and Guidelines. Typical factors that are addressed include: the timeliness, geographic and technical relevance, precision, completeness, representativeness, consistency, reproducibility, sources, and uncertainty of the information (for example, data, models, and assumptions).


This brief introduction to data quality and variability for carbon footprints will hopefully give you some indicators to look for the next time you read one of these studies. 
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Wednesday, April 19, 2017

Carbon Group Post 1: Why Climate Change Matters

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Structural Materials and Global Climate: Why Climate Change Matters

The Carbon Task Group of the Structural Engineering Institute’s Sustainability Committee has spent years studying the ways structural materials and systems affect climate change. This is the first of a planned series of blog posts on topics discussed in depth in our forthcoming technical report.

Why should we care about climate change? How bad could it be? Warmer winters will be nice, right?

We all know what’s happening. Among other things, people are burning a lot of fossil fuels—coal, oil, gas—sending unprecedented quantities of carbon dioxide and other greenhouse gases into the atmosphere. These heat-trapping gases are raising the temperature of our air and oceans, and increasing the ocean’s acidity. Polar ice is melting, contributing to sea level rise. Some regions are experiencing more intense storms and more frequent droughts. Coral reefs are dying. But so what, we can adapt, you might think. Well, maybe, but it would not be easy and the risks are great.

Even if you don’t live by the ocean or in a place where water shortages may become commonplace, there’s a lot to worry about. Climate change promises to be politically destabilizing, as millions of people find their homes inundated or food supplies threatened. They will need to resettle, increasing the flow of refugees. Political instability will lead to conflict, and yet more refugees. The Pentagon considers climate change a major risk, an “accelerant of instability” and a “threat multiplier.” We will all be affected.

And changes are coming fast. A recent study found that the United States is likely to reach an average temperature increase of at least 2°C by 2035, nearly 15 years earlier than the prediction for the globe as a whole, and that there’s at least a 50-50 chance that the northeast could reach this dubious milestone in only 10 years (Figure 1). Coastal cities such as Boston are talking about taking extreme measures to control advancing seas, such as constructing a four-mile-long, 20-foot high, barrier wall around the harbor to protect the low-lying areas of the city (Figure 2).

But the most unsettling changes are not inevitable. We still have a short amount of time to mitigate such worst-case outcomes, and structural engineers have a key role to play. We will explore what we can do in coming blog posts, so stay tuned.


Figure 1 shows the range of climate model predictions for the timing of temperature increases in the northeastern United States, the United States as a whole, and the world as a whole. The vertical axis represents the percentage of climate models that predict a given temperature will be reached by a given year.



Figure 2 shows a proposed 4-mile-long barrier wall to protect the city of Boston (Boston Globe, 17 February 2017).
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Monday, March 21, 2016

2016 Geo-Structures Presentations

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The ASCE-SEI Sustainability Committee and the ASCE Geo-Institute Sustainability in Geotechnical Engineering Committee had a very successful 2016 Geo-Structures Congress. We are happy to report that the two committees had representation at five sessions; they presented on various aspects of sustainable design. Since one of our main committee goals is to spread the word on sustainable design aspects that the practicing structural engineer can put to use, we’re posting the presentations here on our website. Have any questions on these presentations or on how to make your designs more sustainable, please comment below or contact Dave DeLong. Online copies of all of the following presentations are available here.

Track: The SEI Climate Action Initiative

‘Introduction/The Role of the Structural Engineer’ by Jim D’Aloisio

Raise awareness of the importance of climate change mitigation and adaptation by structural engineers, and share mitigation and adaptation ideas and strategies with the structural engineering community

’Mitigation of Emissions During Construction’ by Megan Stringer

My presentation discussed how engineers can quantify and reduce the embodied energy and emissions from buildings. 

‘Rationale for Concern’ byMark Webster

'Mitigation of Emissions During Building Operation'  by Dave DeLong

'The decisions that structural engineers make in detailing the building envelope can influence the building's R-value by a great degree. By detailing to increase this R-value, structural engineers can reduce the heating and cooling loads - and, as a result, the carbon impact - of the building over its service life

Track: Disaster Resilience – Indispensable for Sustainable Design

‘Introduction / Incorporating Life Cycle Assessment with Disaster Resilience’ by Tona Rodriguez-Nikl

An introduction to the session, putting forward the argument that disaster resilience must be considered as part of sustainable design. / A summary of recent efforts to integrate life cycle assessment with disaster risk methodologies. The goal of these studies is to quantify how different levels of disaster resistance affect environmental life cycle impacts.

‘Resilient Design Strategies for Structural Engineers

My presentation discussed resiliency, why it matters to structural engineers and how engineers can design resiliently. The presentation also reviewed current legislation, organizations, and rating systems that deal with resiliency. 

‘Learning to Survive: A global comparison of recovery from disasters’ by Erica Fischer and Sal Gimbert-Carter

Disasters have catastrophic impacts on countries economically, socially, culturally, and politically. This presentation compares how three different countries responded to three different disasters: 2004 Summatra Earthquake and Tsunami in Indonesia, 2005 Hurricane Katrina in New Orleans, and 2010-2011 Christchurch Earthquake Sequence in New Zealand.

 
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Monday, March 14, 2016

How do United States design codes incorporate disaster resilience and adaptation to climate change?

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In the United States, building codes govern the planning, design, construction and often operation of our buildings. Codes encompass sets of regulatory data that specify the minimum standards by which we must construct our building and non-building structures. The International Building Code (IBC) is widely used in the United States. It reflects a set of rules on how we should build and what type of techniques, materials and processes we should follow. The result is a safe and permitted structure. The IBC, however, does little to regulate building behavior with regard to disaster resilience and climate change adaption.


Disaster Resilience and climate change adaptation strategies are often implemented by choice from available disaster mitigation programs. These programs are categorically divided into voluntary and mandatory programs. Most, however, are voluntary. Elective programs encourage owners and communities to implement design choice that can reduce the risk of damage from natural disasters while mandatory programs seek to enforce and enhance standards through law. In the same way that governments adopt model codes as law (e.g. the IBC), mandatory mitigation programs provide language for state and local government and Federal Agencies to adopt as law with the objective of reducing losses from natural hazards. HPBRS (High Performance Building Requirements for Sustainability) is a mandatory program ready for adoption. Often such requirements are formatted to facilitate adoption as amendments to the current IBC. Still, such mandatory amendments need to be adopted by local and state officials for progress to be made. And even when done so, the increased disaster resistance and improved durability are considered enhanced sustainability requirements within such amendments.
 
Disaster mitigation programs for adoption are technically either prescriptive-based or performance-based. The simplest approach is prescriptive, where one specifies how to build using rules that engage the engineer with what the design must achieve, avoid and/or eliminate. Prescriptive guidelines are built upon assumptions about the nature of the hazard, the structural response, and the design objectives. Design professionals must carefully evaluate these assumptions again the objectives of the project before proceeding. Performance-based approaches state what the final results need to be and how it will be measured. It does not specify how those results are to be achieved. Such approaches can be achieved through probabilistic assessments of hazards and consequential damage whereby a cost-benefit analysis to balance increased costs with improved structural resistance is provided. The probabilistic process can be repeated to achieve varying levels of robustness. This can help optimize the balance between additional materials required for construction and probable savings from repairs during the facility’s lifetime. Despite superiority of the performance-based approaches, many of the programs discussed are prescriptive. They are relatively simple and therefore have greater likelihood of being adopted by owners and government agencies.
 

Much is happening to incorporate disaster resilience design strategies into standards and codes. Engineers continue to encourage the use of LEED and life-cycle assessment. A performance-based design standard for fire protection is to be published as a joint venture through the Fire Protection Committee of ASCE/SEI and NFPA. The AISC Design Guide 19 for fire design is also available. Other developments in FP can be found in ASCE/SEI/SFPE 29-05 Standard Calculation Methods for Structural Fire Protection 2005 and ACI 216.1-07 Code Requirements for Determining Fire Resistance of Concrete and Masonry Construction Assemblies, July 2007.
 
Established in 1969, the National Institute of Standards and Technology (NIST) Engineering Laboratory has for many years supported numerous national programs with the ultimate aim of identifying improvements in codes, standards, and practices. NIST supports the adoption of disaster risk management in the code and is currently funding researching in following topics:
 
  • Application of Database-assisted Design within the framework of the wind tunnel methods.
  • Risk Targeted Earthquake to replace the Maximum Considered Earthquake in an effort to make risk the common denominator in design, instead of hazard.
  • Structural load improvements.
  • Methods for estimating wind speeds based on the logarithmic law long.
  • Use of Saffir-Simpson hurricane scale for design wind speeds; database assisted design; and wind directionality effects.
  • In conjunction with NRC, criteria on hurricane-borne missile speeds.
  • Guidelines for including manufacturing into LCA.
Seismic events and weather-related disasters effect developed and developing countries, with much devastation faced by the rapidly growing low-income and lower middle-income countries (WBG, 2014). A lack of code compliancy along with failure to address issue of building and land-use regulatory policy in developing countries has lead to rapid urbanization without regard to disaster risk. The Global Facility for Disaster Reduction and Recovery (GFDRR), a World Bank-managed fund supported by 21 donor partners, the European Union, the World Bank, and the United Nations, is aiding in the provision of advanced knowledge and advice on disaster risk management. During the 2012-2013 fiscal year, GFDRR helped over 80 developing countries to better identify, prepare for, and recover from natural disasters (WBG, 2015). Assistance is provided across five areas: 1) risk identification; 2) risk reduction; 3) disaster preparedness; 4) financial protection for countries and people; and 5) resilient recovery when disaster does strike. The GFDRR aims to conventionalize disaster risk management and recovery into all country development polices and plans. A huge step towards this goal is the commitment of the International Development Association (IDA) to review all country strategies and operations for climate and disaster risks. (WBG, 2015).
 
Spending time and money up front to reduce the likelihood of loss during a natural disaster can bring significant benefits to owners and communities. These benefits are many and include lowering insurance costs, raising property values, providing security to residents, maintaining a consistent tax base, and minimizing the cost of disaster response and recovery. No community can ever be completely safe from all hazards, but resiliency planning gives communities the knowledge and abilities to protect themselves before and mend themselves after a disaster. Structural engineers and our supporting organizations play a vital role in resilient communities. As the nation moves forward to incorporate disaster resiliency as a national priority, standards organizations will be expected to play a critical and complementary role in achieving that goal.
References
Rodriguez-Nikl, T., Comber, M., Foo, S., Gimbert-Carter, S., Koklanos, P., Lemay, L., Maclise, L., VanGeem, M., and Webster, M. (2015). “Disaster Resilience and Sustainability”, SEI Sustainability Committee, Disaster Resilience Working Group, http://tiny.cc/DisResSust.


"Standards and Codes: Disaster-Resilient Structures and Communities." NIST. NIST Engineering Laboratory, 11 Jan. 2011. Web. 20 Oct. 2015.


“Improving Building Code Implementation and Compliance for More Resilient Buildings in Developing Coutnries: Considerations for Policy Makers.” The World Bank, October, 2014. Web. 21 Sept. 2015.
"Helping Countries Better Prepare for and Manage Disaster Risks, Climate Change." The World Bank, 30 January 2014. Web. 17 Sept. 2015.

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