Life cycle assessment quantifies the environmental impacts of a building material or product throughout its entire life.

This includes impacts during extraction, processing, manufacturing, transportation, use, reuse, maintenance, recycling and eventual disposal.

The life cycle assessment process is set out in ISO standard AS/NZS ISO 14040. Under the process, a product, a building system or a whole building can be assessed to determine the environmental impact it will have over the whole of its life. The process involves:

• compiling an inventory of relevant inputs and outputs (for example, raw materials and energy)
• evaluating the potential environmental impacts associated with the inputs and outputs
• interpreting the results.

There are a number of life cycle assessment tools and websites, for example:

• BRANZ wall claddings life cycle analysis tool
• the Environmental Choice NZ scheme
• the Eco-hierarchy Tool
• Ecospecifier – see www.ecospecifier.org (Australasia)
• Greenspec – see www.greenspec.co.uk (UK)
• Gabi (www.gabi-software.com) and SimaPro (www.pre.nl/simapro) – two of the most widely used databases for building material examination.

BRANZ wall claddings life cycle analysis tool

The BRANZ wall claddings life cycle analysis tool provides comparisons of 16 commonly-used lightweight New Zealand wall claddings. The four key issues examined are:

• carbon dioxide emissions
• embodied energy
• recyclability
• life cycle costs.

The tool is available for downloading as an Excel spreadsheet. You may accept the default settings when you use it or apply your own weightings to each environmental issue. You may also select as many or as few of the issues as you wish. Although it is somewhat limited by the materials available for comparison, it nevertheless provides a useful comparison of key environmental performances.