Timber as a sustainable building material

B+C Design Construct

Bala Residence

Sustainable building materials

• The materials used to build our homes can have significant health and environmental effects

• When choosing materials for environmentally sustainable buildings we must consider:

1. The processes used to harvest raw material

2. Processing of material3. Transport to site

So, what is timber?

• Timber is a material which can be used for building or carpentry and is derived from trees. It is organic and renewable and can be used in a wide range of applications.

• In order to make best use of timber in environmental buildings we must understand how timber is produced and how its natural properties effect it as a building material.

The resource

The majority of Australian timber production is from managed forests. There are two broad classifications of managed forests:1.Managed Native Forests2.Plantations

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Source: FWPRDC Education Resource Package

-Construction Component

Managed native forests

Managed for:• Species conservation• Water harvesting• Timber harvesting• Public education• Recreation

Plantations

In plantations trees are specifically planted and nurtured for timber production.

A plantation coup

• Most commonly plantations have only a single species is planted. However plantations can be several species.

Timber - environment

1. Growing and harvesting timber • Low energy of production• Carbon stored in timber away from atmospheric cycle

2. Managed Forests• Plantations - single species farmed for timber• Native forests managed for many uses

species conservation / biodiversitywater harvestingtimber harvestingpublic educationrecreation

Carbon cycle

Growing Trees absorb lots of C02Carbon IN

Carbon OUT

Large trees die by losing leaves then falling over

Over long term

Carbon in ~ carbon out

Environmental considerations

New trees planted

Managed Native Forest Plantation

Growing TreesHarvesting Removes Carbon

C02

IN

C02

OUT

Over long term Carbon removed from atmosphere >

carbon released into atmosphere

Harvesting timber

Timber grows on trees!

“All plant material consists of cells of various shapes and arrangements. The presence of the very complex organic substance known as lignin is an essential feature of those plants being described as woody. It bonds the various types of cell together, producing the degree of rigidity that is associated with wood, and enables woody plants to attain their large size”

(Wood in Australia, 1983)

Timber is cellular!

rays

rays

cells

fibres

vessels

hardwood

earlywood

rays

latewood

softwood

Cellular construction of timber

• The cellular construction of timber effects its properties;

• Cells are bound together to form fibres, and have the main direction of orientation in the longitudinal direction. This makes timber a fibrous material.

Grading for forest products

Grading for forest products

• Only some part of any log or tree can be used for sawn or veneer products. The remainder can be used for sheet products, paper or cardboard.

• Sawlogs – Approximately 30% of the tree goes to producing sawlogs

• Pulp• Veneer

• Timber is a light construction material with a high strength to weight ratio.

• Economic and easy to use, it is available as a structural and appearance product, and suitable for a wide range of uses.

Hardwood in a drying yard

Some considerations when selecting materials!

• Clean materials• Healthy Materials• Renewable materials• Natural materials• Abundant materials• Durable materials• Resource efficient materials and material

usage• Reusable and recyclable material• Energy Efficient material

Timber is a clean material

• Using Life Cycle Assessment timber can be seen to be a clean material relative to other building products like concrete and steel.

Life cycle impacts of major building materials.

Source: ATHENATM Sustainable materials Institute, undated

Timber is a healthy material

• Timber is a natural, organic and healthy material, and its production helps clean the environment.

• Timber can be chemically treated to enhance performance in some ways, (appearance, durability), in most cases only a small amount of this chemical is used.

Timber is a renewable material

• Timber is grown and harvested in the natural environment, flows through the economy in many different applications and then returns to the natural environment at the end of its life.

• Managed forests ensure that timber remains in abundance as a building material.

Timber flows through the economy.

Durability issues

• Timber has natural durability to some hazards. This can be due to the chemicals stored in the wood structure, or in some cases it may be due to the wood structure itself.

700 year old grain store, France

Durability issues

• Hazard - biological or physical

• Natural durability of timber

• Treatment of Timber

• Design for Durability

• Fire

Durability

Biological/ Physical Hazards:

WeatheringFireChemicalFungiTermites / borersMarine

Timber:

SpeciesNatural durability of heartwood

Design DetailingMinimises exposure to hazards

Treatmentenhances durabilityof sapwood

Maintenance ensures protection remains functional

Timber can be durable by design• Correctly specify species and treatment to match function and

environment• Keep timber dry• Protect timber from weathering• Detail connections to avoid trapped water• Use corrosion resistant fasteners• Isolate timber from termites - inspect regularly• Maintain timber regularly -

use good quality paints, stains, WRP’s• Protect structural timber from fire

Timber is resource efficient

• All parts of a tree can be used in various applications, and care and good design can ensure greater resource efficiency when using timber.

Reusable and recyclable material

• There is much recycled timber available for reuse, and local council DCP’s and Green building rating tools encourage reuse.

500yr old recycled timber, France

Other recycling options

• Waste timber can be mulched or chipped for energy or heat recovery as biomass.

Timber is an energy efficient material

1.5 235

435

0

100

200

300

400

500

Fossil fuel energy (MJ/kg)

Rough sawn timber Concrete Steel Aluminium

Timber uses less energy to make!

Summary

• Timber is a renewable resource;• Timber can be made more durable through good

design and treatment;• Timber is a low embodied energy material, with

low life cycle impacts;• There are various reuse and recycle options;

• Timber has an important role in a sustainable built environment.