Currently 10 to 20% of life cycle energy on average is used during the extraction of raw materials and construction of a building or construction product. The remainder is consumed during its operation.

Monthly operational energy consumption in buildings needs to be reduced because of changes to Building Regulations and the rising price of energy as well as concerns about climate change mean. This is making everyone is thinking more about the distinction between upfront energy consumption and in-use energy consumption.

As buildings use less and less energy, then the focus shifts to reducing the proportion used by extraction and construction. All of this impacts on design decisions and this is where Life Cycle Assessment comes into play.

Life Cycle Assessment is a structured methodology for compiling and evaluating the environmental impacts and the primary energy demand of a product system throughout its life cycle.

Life Cycle Assessment can be applied to any product or process, assemblies, entire HVAC systems or even whole buildings. A new guide from BSRIA has been published which provides an introduction for those who are new to the concept or who need a reminder of the basics.

It divides the LCA process into four key steps:

1. identify goal and scope by defining boundaries and the functional unit
2. model the processes and resources involved in the system, collate the life cycle inventories of these processes and resources and generate any new inventory required
3. adjust life-cycle impacts in terms of mid points and endpoints
4. evaluate and interpret results and generate the report for decision-making.

The guide uses a single worked example split into 12 parts to illustrate how the process works. It is a building services oriented example.

Life cycle assessment is already standardised through a range of ISO documents, including ISO 14040:2006 and ISO 14044:2006, which cover principles, framework requirements and guidelines and, published six years later, ISO/TR 14047:2012 and 14049:2012, which help with applying the earlier standards the impact assessment and inventory analysis.

The benefit for anyone involved in construction, design or manufacturing process is to use the protocols to find environmental hotspots - key stages that have disproportionately high environmental impacts - so these can be reduced.

It's also used to provide information to decision-makers and politicians to help them form strategic plans and to generate information about the environmental impact of particular products or classes of products for marketing or behaviour change purposes.

It can be used to compare the relative environmental impact of different products that perform the same function. It could also be used to compare different primary construction materials such as the benefits of timber frame versus steel frame buildings, or different design approaches such as heavy construction with a high degree of thermal mass compared to a lightweight design that might have higher heating and cooling loads over its lifetime.

These metrics, along with ecological footprint analysis, will become increasingly important as tools in decision-making and policy formation.

LCAs do not solve every problem: they must be run alongside technical assessments and cost benefit analyses. But they must be transparent to enable the reader to trace the path of the argument through the various levels of analysis and assessment.

This guide is extremely useful and thorough and deserves to be widely adopted.