Sustainable Design

Overview

The Sustainable Design Committee seeks to establish/advocate the role of the engineer in the developing field of sustainable design. The committee holds monthly meetings to discuss the role of the engineer in the sustainable design process, to provide guidelines for the contributions of the engineer to the sustainability of a project, and to review current projects and trends in sustainability.

For inquiries email: sustainable@seaonc.org

Publications and Presentations
Sustainable Resources
Sustanable Design Information - Materials

Publications and Presentations

The Sustainable Design Committee has written several papers focusing on structural engineering in sustainable design. They have also hosted speakers to discuss important issues concerning structural engineers and sustainability. Below is a list the committee's latest publications and presentations.

Publications

Presentations

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Sustainable Resources

The Sustainable Design Committee has worked to compile what they feel is useful information regarding sustainable buildings. This information is intended to be used by designers, builders, and owners when they are making sustainable design decisions related to structural engineering.

General Websites:  

USGBC
Build It Green
AIA Committee on the Environment (COTE)
AIA COTE San Francisco - Events
Assembly Bill - 32
2030 Challenge
Federal Green Construction Guide for Specifiers
SEI Sustainable Design Committee

Life Cycle Assesment Tools:

Athena Institute
BEES
ATC - 58

For material specific links and information, refer to  Sustainable Design Information - Materials.

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Sustainable Design Information - Materials

Concrete

Concrete is the most widely-used building material. The world’s consumption of concrete per capita has tripled in the last fifty years, due to the rapid development of countries such as China and India, as well as the continued demand to replace, repair and retrofit existing structures. It is estimated that 7-8% of global CO2 emissions result from cement production and curing.

A typical concrete mix consists of 10 to 15 percent cement, 60 to 75 percent fine and course aggregate and 15 to 20 percent water by volume. In some mixes, 5 to 8 percent of the concrete will consist of entrained air. The ratio of water to cement in the mix is of critical importance because it affects the strength and workability of the concrete. Structural concrete typically has a w/c ratio ranging between 0.35-0.45. In green design, the cement is commonly replaced by fly ash or ground granulated blast furnace slag. Replacing cement with fly ash and/or blast furnace slag can greatly reduce the environmental impact of concrete construction. However, if no other modifications are made to the mix design, the substitution of fly ash or slag can result in delayed strength gain. However, recent studies have shown that a reduction in the w/c ratio can produce 28-day strength gains in a 50% cement replacement mix comparable to a typical 15% replacement concrete mix design. The addition of fly ash and slag provides a better workability in the concrete which partly offsets the lower water content of this type of mix, however a plasticizer admixture may need to be specified with these reduced w/c ratios.

In addition to utilizing cement replacement in concrete mixes, there are many emerging sustainable alternatives to concrete aggregates that utilize recycled or natural materials. Ongoing developments in improved batch plant efficiencies and alternative concrete products provide new avenues for achieving sustainable concrete design.

Refer to the following links for more information on sustainable concrete design:
Concrete Carbonation
High Replacement Fly Ash in Masonry Grout
Slag
Cement Replacement Materials

Steel

Steel is widely recognized as one of the leading materials in sustainable construction. By default, steel is a highly recycled material. The common practice of converting scrap metal back to new steel saves the steel mill time and money versus starting with virgin steel. Typically the recycled content produced in the U.S. is between 90-99% total recycled content (70-95% Post Consumer, 5-20% Pre Consumer), but can vary from mill to mill. The amount of recycled content is largely dependent on the type of process which the mill uses to produce its steel (EAF-Electric Arc vs. BOF-Basic Oxygen), this will be discussed in greater detail below. Reinforcing steel, used with Concrete Design, also contains a high content of recycled material, but usually somewhat less then wide flange sections. With careful detailing, steel can also lend itself to future adaptive re-use. One way it does this is in giving a building which has lived out its useful life a chance to be repurposed through deconstruction and reuse. In addition, through the use of millwork and prefabrication, work on-site can be minimized, thus saving on energy, material waste, and site space. As with any building material, designers should make themselves aware of the embodied energy costs of producing steel and delivering it to a job site. It is not recommended to specify that a minimum recycled content for steel be met. This could result in a requirement that the steel would come from a mill a farther distance away from the site than a more local mill with less recycled content, thus adding unintended transportation impacts.

Refer to the following links for more information on sustainable steel design:
Recycled Steel Content

Wood

Wood is used throughout the world and has many characteristics that make it an inherently "green" building material.

Wood is a bio-based material and is entirely renewable. Trees extract carbon dioxide from the atmosphere and the carbon is stored in the wood building products. Wood has low embodied energy compared to most other structural material. The energy consumed in managing forests, harvesting trees, milling timber and transporting lumber to job sites is relatively small. Wood fares exceptionally well when comparing the manufacturing impacts of building materials such as solid waste generation, air and water quality impacts, and greenhouse gas creation. Further, wood is both recyclable and reusable.

A structural engineer endeavoring to design responsibly with wood should consider the following sustainable initiatives:

  • Specify wood products that come from regional, sustainably managed forests. Responsible forest management is the key to preventing potential adverse environmental impacts associated with the harvesting of timber from forests. For more information click here.
  • Utilize wood efficiently. Consider using prefabricated building components, engineered wood products and advanced framing techniques. For more information click here.
  • Design durable structures that are resistant to deterioration, and can be altered and adapted to new uses and loading conditions. Increasing levels of carbon dioxide in the atmosphere from the consumption of fossil fuels has been recognized as a cause of accelerated climate change. To effectively remove carbon dioxide from the atmosphere on a sustainable basis, mature trees must be periodically harvested and milled into building products that will endure for many decades. This is referred to as "carbon sequestration" since carbon becomes a permanent and integral part of the building products. The key to effective carbon sequestration is building wood structures that will endure for many decades, even centuries.
  • Specify non-toxic preservative treatments when appropriate or naturally occurring decay-resistant species such as Redwood, Cedar and Cypress.
  • Require that construction site waste and demolition debris be sorted and recycled, or used as bio-fuel.

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