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  Life Cycle Assessment (LCA)

Introduction to LCA

LCA is a tool for quantifying the inputs and outputs of a product, service (or organisation) and calculating the associated potential environmental impacts. LCA is a systematic process, where the system under investigation is defined as a collection of operations across one or more stages in the product life cycle. This system is then linked to other systems supplying and transporting inputs and carrying away outputs, all of which is considered within the assessment.

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Example of a product life cycle.Example of a product life cycle.

An LCA provides a comprehensive picture of the flows of energy and materials through a system. Results are presented in terms of the system function so that the value of the function can be balanced against the environmental effects with which it is associated.
The results of an LCA help identify opportunities for improvement and to indicate more environmentally-preferable options, for example, through comparison of alternative building designs.

LCA applied to buildings

The application of LCA to buildings is covered in international Sustainability in building construction and European Sustainability of construction works standards. These divide the life cycle of a building into four stages, being:

Product stage - includes processes prior to building handover such as raw material supply, transport and manufacture of products up to the manufacturers' gates.

Construction stage - includes transport to and activities on the construction site. This stage includes transport and any onward processing, if necessary, of wastes or landfilling of wastes that are generated during transport and installation. The manufacture of materials and products that become waste is also included here, rather than in the Product stage.

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Depiction of a building life cycle.

Use stage - includes activities required to enable the building to maintain its level of function including maintenance, repair, replacement and refurbishment. This also includes supply of water to, and treatment of wastewater from the building, as well as supply and use of energy.

End-of-Life stage - includes deconstruction or demolition of a building, transport of materials, and processes necessary for recycling or disposal.

Each of these stages is further sub-divided into discrete, numbered modules, shown below. An information module called module D may also be separately calculated and reported, which summarises environmental benefits or loads that may accrue as a result of choices and actions during the life cycle of a building. Examples include substitution of primary materials as a result of availability of secondary materials from recycling at building end of life, and substitution of Grid electricity due to export of site-generated electricity to the Grid during the Use stage.

A building level assessment should typically consider the stages shown below (with Module D being optional), but there may be good reasons why some modules within these stages are excluded. Module D should be reported separately since it represents potential benefits or loads beyond the life cycle of a building being evaluated.

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Stages and modules of the building life cycle 

For further information about building LCA and the whole building whole of life framework, download the BRANZ SR349 report in Information.