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Metals Compared to Wood for Sustainable Construction
1/11/2012
Alexis Karolides, AIA
Metals have become such a common element in so many building applications, from nails to plumbing fixtures, that it would be hard to imagine building without them. Metals are strong, durable, and generally do not cause indoor air quality problems. (Airborne dust from lead paint is a notable exception.)
Sometimes metals are just one of several viable material choices, in which case it is instructive to compare options. Structural framing is one such example. The debate over which is the “greener” framing material—steel or wood—has no unanimous resolution. Although steel is highly recyclable and its raw materials are plentiful, wood is a renewable resource, is recyclable and biodegradable, and has much lower embodied energy than steel (even recycled steel has five times the embodied energy of kiln-dried wood). Wood is also a natural insulator, whereas steel is a conductor. (It is 400 times more conductive than wood.) The “thermal bridging” that occurs at exterior walls where steel studs span from the inside out can halve the overall R-value of a wall with cavity insulation (as compared to the R-value of the same wall framed with wood). This presents a major energy-efficiency problem for steel-framed exterior walls. Providing a layer of continuous exterior insulation, while it does not completely solve the thermal bridging problem, can significantly increase the overall R-value of the steel-stud wall.
On the other hand, steel framing is lighter than wood, more regular and dimensionally stable, and offers the advantage of resistance to insects. It does not require (as wood does) treating the soil with termiticides, and therefore is better for air quality. Steel is easily separated at the demolition site using a magnet, and steel scrap has a ready market. The overall recycled content of U.S. steel (on average for all steel products) is 46%, but this doesn’t account for the steel scrap that is exported (11% of the total manufactured steel) rather than re-manufactured in the U.S.
Both the wood and steel industries have caused serious environmental problems. Clear-cutting forests has caused habitat destruction and siltation of streams (and pesticide-laden, monoculture plantation forests are not much of an improvement). Strip-mining for the iron and limestone used in steel has caused severe erosion, ecosystem destruction, and leaching from tailings piles into water systems. Fortunately, both industries are making environmental and efficiency improvements.
In an application that allows the use of either wood or steel (especially if untreated wood can be used), wood from a certified, well-managed forest would be the most environmentally sound choice. Overall, its manufacturing process uses much less energy and creates less pollution and environmental degradation than mining and processing steel.
The mining and manufacture of other metals presents environmental concerns similar to those associated with steel, and often much more severe. For instance, the embodied energy of copper is about twice that of steel, while virgin aluminum has as much as seven times the embodied energy of steel.
Like steel, other metals used in building are highly recyclable. Although remanufacturing metals uses significant energy, it is much less than the energy and environmental impacts of starting with the virgin resource. Because metals are highly durable and could be recycled indefinitely, their environmental impact (extraction from the earth and the fact that they are nonrenewable resources) is significantly reduced.
Finally, metals offer clear advantages for certain applications. For example, if water collected from a roof surface is to be used for drinking, a steel roof will not leach petro-chemicals into the water, as an asphalt-based roof might. Although stone or clay tile roofing could also be used, their greater weight would require more structural support than the lighter steel.
Alexis Karolides, AIA, the author of this article, is a registered architect and principal with the Rocky Mountain Institute (RMI) in Snowmass, Colorado. This article was adapted from Green Building: Project Planning & Cost Estimating, 3rd Edition, available through RSMeans.
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Thoughts for Today
1/11/2012
Trust in the Lord with all your heart; do not depend on your own understanding.
Seek his will in all you do, and he will show you which path to take. Proverbs 3:5,6 (NLT)
When the body dies, the spirit lives on forever. Where will you spend eternity? Either with God or in
eternal torment. "If you confess with your mouth Jesus, and believe in your heart that God has raised him
from the dead, YOU SHALL BE SAVED!" Romans 10:9
Commit to the Lord, whatever you do, and your plans will SUCCEED!
Prov. 16:3 (NIV) (This really works!!)
There is a lot of talk today about "Real Americans". However, we all have to respect the Native American Indians.
Like the two braves who were visiting New York City for the first time and a little old lady went up to one of them
and asked, "Are you a real Indian?"
"Yes, ma'am," answered the Indian.
"How do you like our city?" asked the lady.
"Fine", the Indian said. "How do you like our country?"
The fire fighters at the local firehouse got a call one night just after they had settled down for some sleep.
"Its an awful fire," cried the caller. "MY HOUSE IS BURNING DOWN!" "Did you throw water on it?" asked the chief.
"Yes!" yelled the caller. "But it didn't help!" "Well," said the chief, "there's no use in our coming over then. That's all we
were going to do." "Goodnight."
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| Elizabethtown High School |
| Schools |
Location: Elizabethtown, KY
Architect: Sherman-Carter-Barnhart Architects
General Contractor: Morel Construction
Date of Project: Spring 2004
Project Value: $3,000,000
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| Fort Knox Dining Hall |
| Government |
Location: Fort Knox, Kentucky
Architect: Burgess & Niple
General Contractor: Messer Construction
Date of Project: Summer 2004
Project Value: $10,109,000
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| Courtyard by Marriott |
| Other |
Location: Dayton, OH
Architect: Braun & Steidl
General Contractor: Messer Construction
Date of Project: March 2006
Project Value $6,000,000
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| Georgetown Fire Station |
| Civic |
Location: Georgetown, Kentucky
Architect: Architecture Plus
General Contractor: David Engineering
Date of Project: Spring 2004
Project Value: $1,200,000
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| Laurel County Central Office |
| Civic |
Location: London, KY
Architect: Sherman, Carter, &Barnhart
General Contractor: Hacker Brothers
Date of Project: May 2007
Project Value: $4,450,000
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| Children’s Medical Plaza |
| Other |
Location: Dayton, OH
Architect: Pinnacle Architects
General Contractor: Danis Building Construction
Date of Project: July 2005
Project Value $8,500,000
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| Bishop-Fenwick High School |
| Schools |
Location: Franklin, Ohio
Architect: SFA Architecture
General Contractor: Turner Construction
Date of Project: Fall 2003
Project Value: $10,000,000
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| Hancock Public Library |
| Other |
Location: Greenfield, IN
Architect: K.R. Montgomery & Assoc.
General Contractor: Meyer-Najem Construction
Date of Project: April 2005
Project Value $6.100,226
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| Winton Hills Academy |
| Schools |
Location: Cincinatti, Ohio
Architect: BHDP Architecture
General Contractor: Dugan & Meyers Construction
Date of Project: Spring 2004
Project Value: $8,213,000
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| Tri-State Orthopedics |
| Other |
Location: Evansville, IN
Architect: Conner & Associates
General Contractor: Weedle Brothers Construction
Date of Project: May 2004
Project Value $3,500,000
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| Bridgewater Mall |
| Retail |
Location: Cincinnati, OH
Architect: RSP Architects
General Contractor: Premiere properties
Date of Project: July 2005
Project Value: $11,000,000
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| Deupree Housing Community |
| Other |
Location: Cincinnati, OH
Architect: SFCS Architects
General Contractor: Messer Construction
Date of Project: June 2006
Project Value $10,000,000
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| First Baptist Church Georgetown |
| Churches |
Location: Georgetown, Kentucky
Architect: Harbour Construction
General Contractor: Harbour Construction
Date of Project: Spring 2004
Project Value: $1,400,000
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| Girl Scout's Regional Headquarters |
| Civic |
Location: Louisville, Kentucky
Architect: Luckett & Farley
General Contractor: Whittenburg Construction
Date of Project: Summer 2004
Project Value: $5,800,000
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| Wyann-Pine Grove School |
| Schools |
Location: London, KY
Architect: Sherman, Carter, & Barnhart
General Contractor: Burchfield & Thomas Construction
Date of Project: August 2006
Project Value $5,300,000
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| Heartland Elementary |
| Schools |
Location: Elizabethtown, KY
Architect: Peck, Flannery, Gream, & Warren
General Contractor: Morel Construction
Date of Project: March 2008
Project Value: $13,625,000
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| Cardinal Hall of Fame Cafe |
| Retail |
Location: Louisville, Kentucky
Architect: Ronald J. Gajoch & Associates, Inc
General Contractor: MC Associates
Date of Project: Fall 2003
Project Value: $1,430,000
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| Dayton Belle-Haven PK-8 |
| Schools |
Location: Dayton, Ohio
Architect: Moody-Logan LTD
General Contractor: Staffco Construction
Date of Project: Fall 2005
Project Value: $9,322,524
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| Stewart Elementary |
| Schools |
Location: Cincinnati, OH
Architect: Cole & Russell
General Contractor: GC Contracting
Date of Project: September 2006
Project Value: $4,500,000
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| Salem & Union Chapel Elementary |
| Schools |
Location: Russell Springs, Kentucky
Architect: RBS Design Group
General Contractor: Branscum Construction
Date of Project: Fall 2005
Project Value: $4,512,115
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| Miami Univ. Conservatory |
| Schools |
Location: Oxford, OH
Architect: Woolpert, LLP
General Contractor: Valor Construction
Date of Project: October 2005
Project Value $1,621,000
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| McDonald's Restaurant |
| Retail |
Location: Lebanon Junction, Kentucky
Architect: Architectural Concepts
General Contractor: Coupe Construction
Date of Project: Summer 2004
Project Value: $520,000
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| Chapel Rock Christian Church |
| Churches |
Location: Indianapolis, Indiana
Architect: Arc Design Group
General Contractor: Patterson-Horth
Date of Project: Fall 2004
Project Value $3,500,000 |
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| Woodlawn National Guard |
| Government |
Location: Woodlawn, Ohio
Architect: KZF, Inc.
General Contractor: Shook Building Group
Date of Project: Fall 2004
Project Value $14,000,000 |
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| Pleasant Hill Academy |
| Schools |
Location: Cincinnati, Ohio
Architect: Burgess & niple
General Contractor: Quantum Construction
Date of Project: Spring 2005
Project Value $6,600,000 |
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| Streets of Chester Lifestyle Center |
| Retail |
Location: Chester, New Jersey
Architect: Patrick Marchetta
General Contractor: Continental Building Systems
Date of Project: Spring 2006
Project Value $12,200,000 |
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| Springdale Nursing Home |
| Other |
Location: Cincinnati, Ohio
Architect: PDT Architects
General Contractor: Schumacher-Dugan Construction
Date of Project: Fall 2005
Project Value $7,400,000 |
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| Edinburgh Retail Outlets |
| Retail |
Location: Edinburgh, Indiana
Architect: C70 Builders, Inc
General Contractor: C70 Builders, Inc
Date of Project: Spring 2005
Project Value $4,100,000 |
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