Committee on the Environment

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Is Wood Good?

  • 1.  Is Wood Good?

    Posted 27 days ago

    Wood is great stuff, it is a natural product, renewable, can be shaped, fabricated in many useful objects, and it can become Art. 

     

    But is it environmentally responsible to use it to build large buildings? 

     

    Here on the east coast of the United States many multistory multifamily buildings have been built in recent years utilizing wood almost exclusively as structural members.  The international press has carried news stories describing a number of ground breaking multi-story mid-rise buildings recently utilizing wood with many more in the planning stages.  When these buildings reach the end of there useful life will the wood materials be recycled?  What will be the cost to remove the wood from a large building? - will the wood still be useful?  What is the total embodied environmental and energy cost utilized in transportation, fabrication, and construction when utilizing wood?  If consideration is made for the amount of carbon a tree will extract from the environment over its lifetime what is the cost in terms of the carbon cycle and balance sheet if the wood is not recycled?  Are we just crating a large problem for future generations by using wood?  How will they recycle or dispose of it?

     

    Wood initially is inexpensive - the alternatives steel and concrete are initially more expensive and have higher carbon footprints related to there initial raw material extracting and manufacturing processes.  Steel can be recycled and remanufactured efficiently and economically today.  Concrete can be recycled.  Given the amount of energy (carbon) expended over a lifetime of recycling do these materials provide less of a carbon footprint that cutting large amounts of trees, fabrication of structural and standardized building elements, and construction for wood buildings?  There have been press reports for recent advances in reducing the amount of energy (carbon) to manufacture concrete, its carbon footprint is being significantly reduced.  Given the carbon cost and the initial energy expended to manufacture steel and concrete are they less expensive compared to the cost of wood if those materials can be recycled and wood cannot over time?   

     

    The question is "Is the race to use wood good"?    

     

    Arthur Hall Adams/ARCHITECT/AIA/LEED AP

    AHAdams&Company

    PO Box 1166

    309 Davisville Road

    Willow Grove, Pennsylvania 19090

    p215.659.8844

    f215.659.8873

    www.ahadamsco.com

     

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  • 2.  RE: Is Wood Good?

    Posted 25 days ago
    Mr. Hall,
    I think you have a very good point considering how wood structural products will be recycled in the future.  Considerations like this should be made whenever we as architects make material selections.  I would like to add on to your comment though that this consideration should make us think about how we design for reuse, rather than recycle.  This could be reuse of an entire building, or reuse of building components.  We are ideally positioned to think about design in a new way to consider reuse over demolition and recycling, especially when so many buildings today rarely remain standing until their components reach the end of their life cycles.

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    Paul Bielicki AIA
    Architect
    Applied Building Sciences, Inc. (Firm)
    Charlotte NC
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  • 3.  RE: Is Wood Good?

    Posted 21 days ago
    Mr. Hall:
    To add to your points, there are a number of nagging issues that create real challenges for the functionality of these taller wood projects:
    • Panelized wood systems lack adequate mass to meet acoustic performance requirements resulting in the need for more complex floor and wall assemblies requiring multiple layers of drywall to achieve the performance levels of concrete or masonry construction.  This results in additional reliance on job site coordination and on-site labor and assembly, negating much of the time savings of off site manufacturing.
    • They are more costly than conventional systems with no additional time savings when compared to precast concrete panelized systems.
    • Wood needs extensive concrete and steel connections to have adequate structural strength to handle loads and reduce vibration
    • Large, older trees have been found to grow faster and absorb carbon dioxide more rapidly than younger, smaller trees, writes Adeshola Ore - contrary to the previous view that trees' growth slowed as they developed. Storing large amounts of carbon in forests is absolutely critical to that and the way you do that is you have big, old trees.  These panelized and laminated wood technologies rely on younger growth trees, increasing the environmental impact of multiple harvests while reducing the ability of the forest to absorb carbon.
    • The bottom line:  trees should be left to do what they do best, grow older to most efficiently absorb carbon. 


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    Donn Thompson AIA
    Kenosha WI
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  • 4.  RE: Is Wood Good?

    Posted 19 days ago
    Part of what bothers me about mass timber buildings is the shear volume of lumber involved.  I'm a life-long environmentalist and try to use lumber responsibly in my projects, meaning I provide the bare-minimum structure that suits the needs.  I try to avoid over-sized decorative timber beams, etc, all in the interest in minimizing the volume of lumber required.  (Likewise, I try to avoid overuse of other more energy demanding materials.)  I do think that timber is manufactured in the worlds largest solar factory and therefore think it has a number of advantages over those more energy intensive materials, if used appropriately.  That being said, the amount of lumber in mass timber buildings is objectionable to me.  As my wife likes to say:  "Just because you can afford it doesn't make it a good idea."

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    Patrick Marr AIA
    Patrick Marr, PE, AIA
    Santa Barbara CA
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  • 5.  RE: Is Wood Good?

    Posted 19 days ago
    Arthur,

    Your asking all of the right questions and what your really getting at is the importance of life cycle assessment as a decision making tool for AEC professionals.   I've done a lot of work performing life cycle assessments for buildings and my short answer to the question of "is wood good" would be sometimes.  The real answer is that it depends on a lot of variables that you hinted at such as forest harvest practices, transportation, alternate comparisons and end of life assumptions.

    Your also correct that certainly not all wood is good.  For instance, if you were to compare worst case scenario wood (poorly harvested, shipped long distances, and landfilled or incinerated at end of life) to best case scenario concrete (low cement content, high quality aggregate, hyper local, and recycled at end of life) it would be relatively easy to prove through a life cycle assessment that wood would actually emit more carbon through it's life-cycle than the concrete alternative.   However, if you start to tweak some of those variables wood can quickly prove to be the more environmentally friendly option.

    Unfortunately there is no one-size-fits-all answer to your question.  Wood certainly has the potential to be the more eco-friendly option, but it really depends on forestry practices.  I'd encourage you to check out a few different resources:
    • Open Letter for Climate Smart CLT
      • A great summary of the concerns about the mass timber trend and recommendations for navigating it. 
    • Carbon Leadership Forum
      • University of Washington collaboration dedicated to reducing embodied carbon in buildings.  Lots of tools, resources, and network links.
    • Embodied Carbon Network
      • Knowledge network platform under the umbrella of the Carbon Leadership Forum.  Endless ways to get involved, ask questions, find events, and get connected on all things embodied carbon.  

    Hope this helps!



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    Brad Benke AIA
    Seattle WA
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  • 6.  RE: Is Wood Good?

    Posted 17 days ago
    Raphael Sperry of Arup provided an excellent discussion of this very important topic in our recent ECN Renewable Materials webinar; a recording can be found at this link:
    Webinars | EMBODIED CARBON NETWORK
    Embodiedcarbonnetwork remove preview
    Webinars | EMBODIED CARBON NETWORK
    ECN hosts a six-part annual webinar series based on Focus Group topics. Each session includes 4-5 panelists, who share research, strategies, initiatives and case studies to measure and reduce embodied carbon during design, construction and operation of buildings. See below to register for upcoming webinars and watch recordings of past sessions.
    View this on Embodiedcarbonnetwork >

    Also a discussion of taking carbon-storing materials and systems to scale ... please have a look.  Thx.

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    David Arkin AIA
    Arkin Tilt Architects
    Berkeley CA
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