Every
building material comes with an environmental cost of some sort. However, some
principles can help guide your choice of sustainable materials and construction
systems. Careful analysis and selection of materials and the way they are
combined can yield significant improvements in the comfort and cost
effectiveness of your home, and greatly reduce its life cycle environmental
impact.
The first step in any strategy to use sustainable materials is to reduce the demand for new materials. Rather than knocking down and rebuilding a home, it’s worth trying where possible to renovate or at least reuse materials from the existing home. Consider building smaller, well-designed houses and minimising wastage by using prefabricated or modular elements, for example, and by avoiding unnecessary linings and finishes. During design and construction, incorporate |
approaches that will make it easier to adapt, reuse and eventually dismantle the building. By choosing durable, low maintenance materials, you can minimise the need for new materials and finishes over the building’s lifetime.
The next step is to select materials with low environmental impact. Put simply, a ‘sustainable’ material is one that does not impact negatively on non-renewable resources, the natural environment or human health. Most products have a net-negative impact on the environment; however, it’s important to minimise the negative impacts of any materials you choose. When looking at the environmental impact of a material or product, consider all stages of the life cycle — the upstream stage (materials extraction and manufacture), the in-use or operational stage, and the downstream stage (disposal or reuse).
Life cycle assessment (LCA) is a highly detailed scientific analysis that examines all the life cycle impacts of a product in great detail. An LCA quantifies the majority of known chemical, physical, resource-based and energy impacts of a material or product. It provides us with increasingly more comprehensive and useful assessments of the sustainability credentials of products and materials, allowing better and easier comparisons between products.
Although some progressive housing companies and developers are starting to embrace LCA, a customised LCA may be beyond the scope of many home building or renovation projects. Selecting products with low life cycle impact can be complex as there are many issues to take into account. However, there is decision-making support available.
Eco-product selection databases such as Eco specifier enable you to access information on the sustainability credentials of a broad range of materials and products. Product assessment schemes, many of them based on LCA, allow you to make even more informed comparisons. These include Eco specifier Verified, BREEAM’s Green Guide and Global Green Tag. Linked to such assessment schemes is a range of ecolabels including Good Environmental Choice Australia (GECA), Global GreenTagCertTM and the FSC (Forest Stewardship Council).
Informed decisions about materials and construction systems can significantly reduce the environmental impact of a home without adding to the cost.
The next step is to select materials with low environmental impact. Put simply, a ‘sustainable’ material is one that does not impact negatively on non-renewable resources, the natural environment or human health. Most products have a net-negative impact on the environment; however, it’s important to minimise the negative impacts of any materials you choose. When looking at the environmental impact of a material or product, consider all stages of the life cycle — the upstream stage (materials extraction and manufacture), the in-use or operational stage, and the downstream stage (disposal or reuse).
Life cycle assessment (LCA) is a highly detailed scientific analysis that examines all the life cycle impacts of a product in great detail. An LCA quantifies the majority of known chemical, physical, resource-based and energy impacts of a material or product. It provides us with increasingly more comprehensive and useful assessments of the sustainability credentials of products and materials, allowing better and easier comparisons between products.
Although some progressive housing companies and developers are starting to embrace LCA, a customised LCA may be beyond the scope of many home building or renovation projects. Selecting products with low life cycle impact can be complex as there are many issues to take into account. However, there is decision-making support available.
Eco-product selection databases such as Eco specifier enable you to access information on the sustainability credentials of a broad range of materials and products. Product assessment schemes, many of them based on LCA, allow you to make even more informed comparisons. These include Eco specifier Verified, BREEAM’s Green Guide and Global Green Tag. Linked to such assessment schemes is a range of ecolabels including Good Environmental Choice Australia (GECA), Global GreenTagCertTM and the FSC (Forest Stewardship Council).
Informed decisions about materials and construction systems can significantly reduce the environmental impact of a home without adding to the cost.
embodied energy
Embodied
energy is the energy consumed by all of the processes associated with the
production of a building, from the mining and processing of natural resources
to manufacturing, transport and product delivery. Embodied energy does not
include the operation and disposal of the building material. This would be
considered in a life cycle approach. Embodied energy is the ‘upstream’ or
‘front-end’ component of the life cycle impact of a home.
Choices of materials and construction methods can significantly change the amount of energy embodied in the structure of a building, as embodied energy content varies enormously between different materials. However, assessing the embodied energy of a material, component or whole building is often a complex task. Another significant factor in reducing the impact of embodied energy is to design long life, durable and adaptable buildings.
Choices of materials and construction methods can significantly change the amount of energy embodied in the structure of a building, as embodied energy content varies enormously between different materials. However, assessing the embodied energy of a material, component or whole building is often a complex task. Another significant factor in reducing the impact of embodied energy is to design long life, durable and adaptable buildings.
waste minimisation
Around 42%
of the solid waste generated in Australia is building waste. A lot of energy
and resources go into the manufacture and transport of materials used to
construct a home, yet eventually most of these materials end up in landfill.
Minimising and recycling waste can have significant social, economic and
environmental benefits.
The ‘three Rs’ of waste minimisation — reduce, reuse, recycle — should be applied throughout the design and construction process: reduce (or avoid) demand for materials by renovating rather than demolishing and rebuilding, and building smaller homes that are better designed for your needs; reuse existing materials or building components; and recycle materials rather than sending them to landfill.
The ‘three Rs’ of waste minimisation — reduce, reuse, recycle — should be applied throughout the design and construction process: reduce (or avoid) demand for materials by renovating rather than demolishing and rebuilding, and building smaller homes that are better designed for your needs; reuse existing materials or building components; and recycle materials rather than sending them to landfill.
construction systems
The
combinations of materials used to build the main elements of our homes — roof,
walls and floor — are referred to as construction systems. They are many and
varied, and each has advantages and disadvantages depending on climate, distance
from source of supply, budget, maintenance requirements and desired style or
appearance. Important factors that may influence your choice of construction
system include its durability, life cycle environmental impact, life cycle cost
effectiveness, role in improving thermal performance, and reuse or recycling
potential, as well as local availability of materials and skills needed to
construct the system.
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lightweight framing
Lightweight
framed construction is the most popular construction system in Australia. Steel
and timber, the two most commonly used framing materials, can contribute to the
comfort, appeal and environmental performance of a home. By assessing
environmental impact, structural capability, thermal performance, sound
insulation, fire resistance, vermin resistance, durability and moisture
resistance, owner builders can come to a decision on what is the best option
for their situation.
brickwork and blockwork
Bricks and
blocks are components of durable masonry construction. They consist of high
mass materials with good compressive strength formed into units that can be
lifted and handled by a single worker. Materials used can include brick, stone
(e.g. marble, granite, travertine and limestone), manufactured stone, concrete,
glass, stucco and tile. They vary in environmental impact, structural
capability, thermal performance, sound insulation, fire resistance, vermin
resistance, durability and moisture resistance. Of the many kinds of bricks and
blocks used in modern Australian house construction the most common are made
from concrete or clay.
cladding
Cladding is
a non-loadbearing skin or layer attached to the outside of a home to shed water
and protect the building from the effects of weather. Your choice of cladding
has significant implications for the environmental performance of your home.
Initial environmental impacts such as embodied energy, resource depletion and
recyclability must be balanced against maintenance and durability appropriate
to life span. Many different cladding options are available, some best suited
to specific applications.
concrete slab floors
Concrete
slab floors come in many forms and can play a significant role in thermal
comfort due to their high thermal mass. Slabs can be on-ground, suspended, or a
mix of both. Often a slab will need insulation in order to perform
satisfactorily. Polishing or tiling a slab allows for better utilisation of its
‘thermal mass’. Conventional concrete is responsible for high greenhouse gas
emissions, mostly from the production of Portland cement and the mining of raw
materials. However, this impact can be significantly reduced through the use of
cement ‘extenders’ (e.g. fly ash, ground blast furnace slag and silica fume),
new cements (e.g. geopolymers, magnesium cements), and alternative forms of
concrete (e.g. hemp Crete).
insulating concrete forms
Insulating
concrete forms (ICFs) are proprietary modular units in the form of interlocking
blocks or panels, made from polystyrene or polyurethane foam and filled with
concrete. Substantial thermal mass and structural support is contained within
easily stacked and joined insulation. The sealed nature of the construction and
the high levels of insulation make these units particularly suited to projects
seeking to achieve very high levels of thermal performance, and they have been
used extensively in Europe for homes that meet the ‘passive house’ standard.
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autoclaved aerated concrete
Autoclaved
aerated concrete (AAC) is concrete that has been manufactured to contain many
closed air pockets. It is lightweight with a moderate embodied energy content
and performs well as thermal and sound insulation, due to the aerated structure
of the material and its unique combination of thermal insulation and thermal
mass. AAC is light, does not burn, is an excellent fire barrier, and is able to
support quite large loads. It is relatively easy to work with and can be cut
and shaped with hand tools. AAC comes in the form of blocks, storey-height wall
panels, and floor or roof panels.
precast concrete
Precast concrete
offers durable, flexible solutions to floor, wall and even roof construction in
every type of housing from individual cottages to multi-storey apartments. High
initial embodied energy can be offset by its extended life cycle (up to 100
years) and high potential for reuse and relocation. Common production methods
include tilt-up (poured on site) and precast (poured off site and transported
to site). Each method has advantages and disadvantages, and choice is
determined by site access, availability of local recasting facilities, required
finishes and design requirements.
mud brick
The ideal
building material would be ‘borrowed’ from the environment and replaced after
use. There would be little or no processing of the raw material and all the
energy inputs would be directly, or indirectly, from the sun. This ideal
material would also be cheap and would perform well thermally and acoustically.
If used carefully mud bricks come close to this ideal. Basic mud bricks
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are made by mixing earth with water, placing the mixture into moulds and drying the bricks in the open air. Straw or other fibres that are strong in tension are often added to the bricks to help reduce cracking. Mud bricks are joined with a mud mortar and can be used to build walls, vaults and domes. With its low embodied energy, this ancient construction method has much to commend it.
rammed earth
Rammed earth
walls are constructed by ramming a mixture of selected aggregates, including
gravel, sand, silt and a small amount of clay, into place between flat panels
called formwork. Stabilised rammed earth is a variant of traditional rammed
earth that adds a small amount of cement to increase strength and durability.
Most of the energy used in the construction of rammed earth is in quarrying the
raw material and transporting it to the site. Use of on-site materials can
lessen energy consumed in construction. Rammed earth provides limited
insulation but excellent thermal mass.
straw bale
Straw has
been used as a building material for centuries for thatch roofing and also
mixed with earth in cob and wattle and daub walls. Straw is derived from
grasses and is regarded as a renewable building material. Straw bale walls are
surprisingly resistant to fire, vermin and decay. Finished straw bale walls are
invariably rendered with cement or earth so that the straw is not visible. The
final appearance of rendered straw bale can be very smooth and almost
indistinguishable from rendered masonry, or it can be more expressive and
textural.
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green roofs and walls
Green roofs
and walls are building elements designed to support living vegetation in order
to improve a building’s performance. Also known as ‘living’ roofs and walls,
they are emerging as important additions to the palette of construction
techniques for creating healthy, ecologically responsible buildings. They can
contribute to thermal performance, stormwater management, biodiversity
conservation and local food production. A green roof is a roof surface, flat or
pitched, that is planted partially or completely with vegetation and a growing
medium over a waterproof membrane. They may be ‘extensive’ and have a thin
growing medium with groundcover vegetation, or ‘intensive’ and have soil 200mm
deep or more supporting vegetation up to the size of trees. Green walls are
external or internal vertical building elements that support a cover of vegetation
that is rooted either in stacked pots or growing mats.
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green materials basics
When considering the
environmental properties of materials, look for materials that are abundant,
non-toxic, have low embodied energy, and meet or exceed regulations.
You also need to ensure that the material has the right physical properties to get the job done and that it won’t drive up costs.
You also need to ensure that the material has the right physical properties to get the job done and that it won’t drive up costs.
ools for green material selection
Having access to good
materials data is critical for making these trade-offs. The Eco Materials
Adviser tool, available as part of Autodesk Inventor, helps inform material
selection early in the design process. It is based on a comprehensive materials
database from Grant Design and provides data about a material’s embodied
energy, embodied CO2, embodied water, cost, RoHS compliance, and physical
properties.
embodied energy of materials
A material’s embodied
energy is the energy that must be used to extract, transport, and process the
material. For a product that doesn’t require energy during use, like a chair,
the material’s embodied energy is often the biggest source of carbon footprint
and environmental impact.
A great way to reduce embodied energy is to specify recycled materials for your designs. For example, using recycled aluminium can cut embodied energy by 90%. If you’re using recyclable materials, you’ll also want to design your product to ensure those materials can be recovered at the product’s end of life.
A great way to reduce embodied energy is to specify recycled materials for your designs. For example, using recycled aluminium can cut embodied energy by 90%. If you’re using recyclable materials, you’ll also want to design your product to ensure those materials can be recovered at the product’s end of life.
health impacts of materials
Materials can sometimes
also have negative health impacts, and some materials are regulated for this
reason. For example, electronics sold in Europe need to meet the Restriction of
Hazardous Substances Directive (RoHS). You can avoid health impacts by avoiding
toxins, clearly labelling them when they are used, and designing-in product
safeguards like child-proof lids.
tools to identify environmental properties of materials
To find data on the
environmental properties of materials, you can use databases published by
companies like Grant Design. The Eco-Materials
Adviser tool within Autodesk Inventor has an Eco-Impact dashboard which
displays data from Grant Design on embodied energy, carbon footprint, embodied
water, end-of-life options, and RoHS compliance.
lifecycle assessment for materials analysis
Conduct lifecycle
assessment (LCA) on your design to dive into more detailed analysis that can
help inform material choice. While more time-consuming, LCA usually includes
more nuanced data on variables like ozone layer depletion, air pollution, water
acidification and eutrophication, land use, Eco toxicity, and carcinogens.
Every pound of material that you save in your product saves much more waste and material upstream. Material Inputs and Ecological Rucksacks are closely related concepts that provide a tangible short-hand for understanding this larger ecological impact of the products and materials around us, and can help understand the importance of light weighting.
An item’s Material Input (MI) is the total quantity (in kg) of materials moved from nature to create a product or service. For example, you have to dig up and dispose of about seven kilogram of material to make one kilogram of virgin steel. The Ecological Rucksack is the Material Input minus the actual weight of the product, and highlights the hidden material flows.
These figures are based on a life cycle approach from the “cradle” to the point when the product is ready for use. They seek to quantify material inputs derived from raw materials use (including minerals, fuels, and biomass), earth movement, water, and air.
This concept originated with Friedrich Schmidt-Bleak from the Wuppertal Institute for Climate, Environment and Energy in Germany.
Every pound of material that you save in your product saves much more waste and material upstream. Material Inputs and Ecological Rucksacks are closely related concepts that provide a tangible short-hand for understanding this larger ecological impact of the products and materials around us, and can help understand the importance of light weighting.
An item’s Material Input (MI) is the total quantity (in kg) of materials moved from nature to create a product or service. For example, you have to dig up and dispose of about seven kilogram of material to make one kilogram of virgin steel. The Ecological Rucksack is the Material Input minus the actual weight of the product, and highlights the hidden material flows.
These figures are based on a life cycle approach from the “cradle” to the point when the product is ready for use. They seek to quantify material inputs derived from raw materials use (including minerals, fuels, and biomass), earth movement, water, and air.
This concept originated with Friedrich Schmidt-Bleak from the Wuppertal Institute for Climate, Environment and Energy in Germany.
basic material input data
Industrial products often
carry rucksacks that are about 30 times their own weight. So only about 5% of
the non-renewable natural material disturbed in the ecosphere actually ends up
in a technically useful form. For example, the ecological rucksack of a
personal computer is about 200 kg per kg of product (Schmidt-Bleak, Man stein,
& Gerhard, June 1999). The table below contains Material Input factors for
some common raw materials used in industrial products.
using material input data
To calculate the Material
Input of your product, multiply the mass of each material you use by its
Material Input factor, and then sum these values.
Considering the Material Input per Service Unit (MIPS = MI/ S) is a good way to compare the resource consumption of different solutions that produce the same service. The metric you use for the service unit (S) depends on your product, but could be hours used or distance travelled. To improve the resource productivity of the solution, you can either increase its service lifetime or reduce its material input.
Considering the Material Input per Service Unit (MIPS = MI/ S) is a good way to compare the resource consumption of different solutions that produce the same service. The metric you use for the service unit (S) depends on your product, but could be hours used or distance travelled. To improve the resource productivity of the solution, you can either increase its service lifetime or reduce its material input.
physical properties of materials
To select greener
materials you need to consider the material’s environmental, cost, and
performance impacts on your design. A material’s performance depends on its
physical properties, and optimizing this is the most important way to reduce
your product’s environmental impact.
Energy use often causes the biggest environmental impact for products that consume much energy during their use, like refrigerators and cars. Creating a lighter weight car can save far more energy than reducing the embodied energy of its materials.
Energy use often causes the biggest environmental impact for products that consume much energy during their use, like refrigerators and cars. Creating a lighter weight car can save far more energy than reducing the embodied energy of its materials.
tools to identify physical properties of materials
The Eco-Materials Adviser
within Autodesk Inventor includes a materials database that is searchable by
properties such as strength, stiffness, density, price, and thermal
conductivity.
Information Source: http://www.yourhome.gov.au/materials