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Embodied Energy in Building Construction
John Herbert
Director
The materials and components used to create new buildings
required the use of energy to mine, process, assemble, and
manufacture and delever to the job site. Its important
because the majority of materials and components are imported.
That energy has already been consumed, so we call it embodied
energy, it is like an energy millstone permanently tied to the
product or material, once the energy becomes embodied, it
already used it is used forever. For a reversible material
such a ferrous and non ferrous metals, additional energy is
embodied during the recycling of the material.
EMSD LCCA software tool provides the energy embodied data
for a range of materials used in construction industry that
can be employeed to calculate the total embodied energy.
Like it or not, sustainability and energy are two sides of
the same coin.
Buildings and Energy
The term Embodied Energy is meant to reflect the energy consumed
during the production of materials and components. For construction
industry we focus on the building structure, predominantly
reinforced concrete (RC), glass curtain wall, and steel are
used in Hong Kong
The production of theses core materials such as concrete components,
glass, aluminium, and steel, all require vast quantities of energy
to produce creating carbon dioxide emissions in the process.
In Hong Kong there are no factories, so materials such as
glass, aluminium, steel must be imported from overseas.
Most of Hong Kong's buildings are constructed using reinforced
concrete, are either cast-in-situ, and the limited use of
prefabricated sections delivered and installed on site.
Reinforced Concrete Cast-In-Situ
The materials for producing reinfored concrete are generally imported
and locally mixed, either on site in a batching plant for large
projects or mixed at concrete plant and transported to site
using concrete mixer trucks. And the rebar for cast-in-situ the
reinforced concrete must also be imported.
The embodied energy for prefabricated components are similar to
other imported components in that the locally used energy cost
is imported with the prefab work.
One challenge for dealing calculating Embodied Energy with imported
materials not covered in the emsd list is the reliance on Embodied
Energy declarations because different countries have different
standards.
Embodied Carbon and Production
Steel and the materials for making concrete are energy intensive,
typically produced overseas and transported to Hong Kong, therefore
the related carbon emissions do not appear in the local inventory.
Therefore publishing the embodied energy and embodied carbon
used in buildings should be encouraged provides a better picture
of Hong Kong emissions.
In a perfect world all the materials would arrive with emodied energy
label, totalling up those figures provides the emodied energy figure,
but real life is rarely that straightforward.
One element for example steel, can be provided by different factories
in different countries, each with a different embodied energy
and the data is often difficult to obtain.
Then some materials for example concrete comprise several different
elements, could be sourced from several different countries.
Often one project will have steel and concrete materials from a
mumber of countries, with different production methods, and
tranportation distances.
Like it or not, sustainability and energy are two sides of
the same coin
-- John Herbert
Embodied Energy in Construction and Demolition Waste
It is often overlooked, after the useful life of a product or material
it is sent to landfill, including the embodied energy millstone
already used in its production.
Demolition of the building or structure does not release the
embodied energy, the energy already used in the creation of the
components and materials, is tied to that material forever.
As one US carpet manufacturer pointed out, its source for raw materials is under the feet of its customers
Under the post consumer waste, post demolition waste should be included,
is important, where possible, that so called "waste" material is not
viewed as waste but as raw materials to repurposed. some examples:
waste concrete - a free resource,can be used as a raw material for
producing new concrete paving blocks (pioneered in Hong Kong);
waste glass (cullet) - a free resource, can be used as a raw
material for producing new glass. Also used as replacement for silca for
producing concrete paving blocks;
waste gypsum board - a free resource, can be used as a raw material
for creating new gypsum board, and can be used as a conditioner
added to soil;
ferrous metal - a free resource, reversible, can be melted
down and used for creating new steel and new steel products;
aluminium (curtain wall) - a free resource, reversible,
can be melted down and used for creating new aluminium products;
With the neccessary expertise for example specifying energy,
water and waste efficient techniques and equipment in buildings
and infrastructure and the specialist analysis techniques to
demonstrate the practical environmental performance Kelcroft
prepares embodied energy studies and reports for developers
and building owners.
Providing embodied energy data to designers, it is hoped
that the information will influence the choice of materials
BEFORE commencing the pre-design/design stage because after
the key decision is made the embodied energy is essentially
fixed forever.
Emodied energy can be influenced, for example choosing
lower volume of higher strength reinforced concrete, means
smaller elements can be used, lowering the quantity of
material required, and therefore the embodied energy.
Materials created from recycled reversible materials,
such as steel, include all the embodied energy from the
scrap material used to produce new steel, in reality that means
the embodied energy increases every time its recycled and reused.
And that means the real quantity of embodied energy in steel,
and other products is infinitely higher than the energy use in
production alone.
For more information about our embodied energy studies and