Timber as a Sustainable Building Material

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Timber as a Sustainable Building Material
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Timbers innate attractions

• Timber is a light, strong material, used in
  building structures for millennia because it is
• Renewable
• Simple to manufacture
• Easy to use and
• Stable and safe.
• Importantly now, it is also a store for carbon.

Woolmers pump house, Tasmania, 1841
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Ease of manufacture

• Producing timber, poles, veneer and engineered
  timber products is a relatively simple, low
  capital process.
• It uses few chemicals, relatively little energy,
  and produces few pollutants.

Staff of a small veneer plant
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Transport

• Logs weigh about 1 tonne/m3.They are transported
  from the forest in trucks.
• Most sawmills are positioned near their log
  supply, so transport distances are usually not
  long.

Logs on landing and being unloaded
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Producing sawn timber

• Logs are delivered to site, stored and then sawn.
  
• Because of the character of logs, only about 35
  of hardwood and 45 of softwood logs are
  converted to timber.
• The remainder is sawdust or chipped.

Hardwood saw mills
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Timber drying (or seasoning)

• The timber is then dried.
• This is either in the open air or in a kiln.
• Air drying is slow and very low energy.
• Air dried material can be finished in the kiln.
• Kiln drying is faster. Often, shaving and sawdust
  fires the boilers that heat the kilns.

Timber in racks for drying
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Dry milling sale

• Dry timber is graded and sorted.
• It can then be moulded to different shapes or
  sold for further processing.
• Often, no other processes are necessary before it
  can be used.

Quality control in a dry mill
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Veneer manufacture

• Logs for structural or decorative veneer are
  delivered to site.
• It may be sawn into flitches and heated in water
  before peeling or slicing.
• Unused section of log are often sawn into timber.

Stacking veneer from a slicer
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Veneer drying and grading

• Once sliced or peeled, the veneer is dried in a
  dryer, before being graded.
• After grading, the veneer is trimmed and can be
  laid up into sheets.

Grading veneer
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Engineered products

• Plywood and LVL are layers of peeled veneer glued
  and pressed together in industrial equipment.
• Nail plating of trusses requires a simple
  hydraulic press and a work space.

Pressing nail plates
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Glue lamination

• Glue laminated material is sawn timber, planned
  to give a smooth edges and adhered with a
  waterproof glue.
• Transport is the only effective limitation on the
  size of glulam members

Prefabricating glulam beams
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Refurbishment recycling

• The ease of initial manufacture translates to an
  ease in
• construction
• refurbishment
• recycling,
• Large sections, joinery and fitting are often
  recycled. Smaller sections may be reused.

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Carbon storage in forests

• During photosynthesis trees absorb CO2 from the
  air, stores the carbon in woody tissue and give
  off oxygen.
• To produce 1 Kg of wood, a tree
• absorb in 1.47 Kg of CO2 and
• returns 1.07 Kg of oxygen to the atmosphere

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Carbon stored in forests

• In 2001, Australia's plantations and managed
  forests stored a net 22.7 million tonnes of
  carbon dioxide equivalent.
• So, they stored more than half of the greenhouse
  gases emitted by all the passenger cars in
  Australia that year.

50 of CO2
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Carbon stored in building

• When logs are converted to timber and other wood
  products, the carbon from the tree is stored in
  the products.
• Timber buildings are carbon stores.

Bus stop, Kings Meadow, Tasmania
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Current greenhouse accounting method

• The current greenhouse accounting method
  calculates decomposition of forest products using
  product service life pools
• Pool 1 - service life 3 years - paper products
• Pool 2 - service life 10 years - pallets, palings
• Pool 3 - service life 30 years - kitchen
  furniture
• Pool 4 - service life 50 years - poles,
  construction materials
• At the end of each pool life, the carbon is
  assumed to return to the atmosphere.
• This may overestimate emission considerably.

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Alternative method

• Establish five service life pools of 3, 10, 30,
  50 and 90 years
• Establish three age groups within each service
  life pool - Young , Mid, and Old
• Wood products then progress through each age
  group with one of five alternatives
• Progress to next age pool
• Leave pool and enter landfill pool
• Leave pool and enter recycling pool
• Leave pool and their carbon is emitted to
  atmosphere
• Long-term storage beyond pool service life

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Alternative Method
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Alternative Method

• The alternative method better reflects what
  happens to wood products.
• The effect on calculated emissions is shown on
  the following two slides.

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Alternative Methods - Conclusion

• A life cycle approach, including consideration of
  the use of residues, storage in service,
  recycling and disposal to landfill has the
  potential to significantly decrease the
  contribution from wood products to Australias
  estimates of greenhouse gas emissions.

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Timber impacts compared to other materials

• Timber is only one of a range of materials
  available for construction.
• All material have an impact and it is possible to
  compare their use in manufacture and use using
  LCA techniques.

Shear connector positions in a glulam beam
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Timber uses less fossil fuel to make
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Timber store carbon. Others release it
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Embodied Energy of Materials
Comparative Energy Use in an idealised structure
where 4 materials have an equal contribution to
the structure derived from Factor 4- Doubling
Wealth - Halving the Resource Use
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Timber has lower embodied energy
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Timber has lower ecological profile
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Timber elements have lower impact

• Embodied energy of differing window frames

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