Life coaching

Life-cycle assessment is defined by the United Nations Environment Programme as “…the process of evaluating the effects that a product has on the environment over the entire period of its life cycle … extraction and processing; manufacture; transport and distribution; use, reuse and maintenance; recycling and final disposal” .

Also often referred to as “cradle-to-grave assessment”, life-cycle assessment (LCA) gives a holistic framework within which to consider environmental impact from the point that the raw material is extracted from the ground to the point at which it is returned to the natural environment (or forms the basis of a further manufacturing procedure).

Using brick as a simple example, LCA would encompass investigation of these stages: quarrying of clay, transportation to the manufacturing facility, the production and firing process, transport to site, construction of the building, maintenance throughout its lifespan, and eventual recycling or disposal. LCA can measure a wide variety of environmental impacts, including climate change potential, acid deposition and ozone depletion (see figure 1).

When aiming to reduce the impact of all these issues in a particular project, a bit of lateral thinking is needed because LCA can often point to some surprising conclusions. It is by definition a holistic process, and so it is unwise to consider any stage in isolation. This requires those involved to look beyond the immediately apparent issues which can disproportionately influence design choices.

For example, the design team of the Integrated Learning Centre at Queen’s University in Ontario, Canada, considered two competing build systems: cast in-situ concrete and structural steel. The initial opinion was that steel would be the most sustainable because it could be recycled. LCA concluded that the concrete system had less impact on global warming, toxicity, solid emissions and energy consumption, but it required greater resource use than the structural steel system. The overall conclusion was that the concrete system had less environmental impact than the structural steel system. The use of LCA turned initial assumptions on their head, and led to a far more sustainable final build.

Construction managers may find similar issues arising in their LCA calculations, particularly given the increasingly complex logistics and supply chain issues occurring on many projects. For example, the debate around on- and offsite construction could be usefully informed by LCA of the products involved.

Before getting into the detail of the process, it’s important first to define the business case for addressing sustainability via the use of LCA. The primary driver is legislation: businesses are increasingly expected to measure their environmental performance and set targets for improvement. Also, a range of legislation is on the agenda – from voluntary benchmarking and reporting to mandatory cap and trade schemes – with the aim of penalising high energy use while rewarding emissions reductions.

To be able to respond to this emerging policy agenda in an informed manner, businesses need to understand the nature and scale of their CO2 emissions as well as their wider environmental impacts. LCA provides a holistic view in an internationally recognised format, and will highlight which areas need to be addressed; going forward, it will allow environmental impacts to be considered alongside other factors in new project planning and delivery.

Changing consumer attitudes mean that clients are now seeking partners that can demonstrate a positive approach to sustainability. Use of LCA demonstrates engagement with environmental issues and can help to attract new business partners, as well as showing commitment to corporate social responsibility. Getting a handle on your impacts will not only help you to reduce future risk but allow you to turn the emerging low- and zero-carbon economy to your advantage.

How does LCA work?

A typical life-cycle assessment consists of these phases:

1 Goal and scope

Initially the key is to relate the goal and scope of the study to its intended application. Rather than look at, for example, bricks and Portland cement in isolation, LCA takes these products in context, as a “functional unit” – in this case it would be 1m2 of masonry wall construction.

Once you have defined the functional unit, lifespan and maintenance requirements can be assessed, as well as the dismantling, recycling and disposal impacts. This functional unit approach allows different construction types to be compared on a like-for-like basis. A steel wall construction could be directly compared with a masonry wall, and the respective mass of materials required (along with all the other impacts measured by LCA) could be compared.

The goal and scope should also address the overall approach used to establish the system boundaries, and determine which processes are included in the LCA. This will largely depend on the goal of the study, as in addition to the

cradle-to-grave approach there are several other methodologies for carrying out partial LCA. (For example, manufacturers that want to make process improvements may use an alternative assessment known as “cradle to gate”, which does not include any impacts beyond the manufacturing phase.)

2 Life-cycle inventory

The second phase involves producing a comprehensive process tree, which shows all inputs and outputs to the defined process. These typically include materials, transport fuel, process fuel, water and emissions to air, water and the ground. Other types of exchanges or interventions such as radiation should also be included. The resulting inventory and its input and output streams should balance in both mass and energy terms.

A common question with LCA is “where should you stop?” for example, should process machinery be included in the inventory? Typically such machinery (and its maintenance) is excluded, although consumables such as saw blades and mould oil should be included. On the materials side, data should be included for 98% of all inputs by mass, which means that low-mass substances can be disregarded (subject to a sensitivity analysis) if their mass is less than 2% of the total process output. Note, however, that this doesn’t apply to very energy intensive substances such as glues.

3 Life-cycle impact assessment

The third phase is aimed at evaluating the environmental impacts associated with the inputs and outputs identified in phase two’s inventory. In the first step, known as characterisation, impact potentials are calculated based on the inventory results, producing a list of quantified impacts for global warming, acidification, and other environmental effects (figure 1). The process can stop here or proceed to the optional normalisation and weighting stages. Normalisation involves all impacts being converted to show the same units of measurement, thus allowing direct comparison between categories. Weighting takes this further still and applies a factor to each category, depending on its relative importance.

4 Interpretation

Phase four consists of checks against phases two and three, and sensitivity and uncertainty analyses to determine whether the goal set in phase one has been robustly met. Having addressed any issues, conclusions can be drafted and, depending on how the data is to be used, an independent critical review may be appropriate. This stage completes the LCA.

Tools and calculations

If the thought of tracing the carbon impacts of your chosen products and strategies right back to their extraction from the ground fills you with foreboding, you may be relieved to know there are tools which can help to take the hard work out of LCA.

BRE’s Green Guide to Specification enables users to select building assemblies on their overall environmental performance over the building’s life. BRE also produces LCA-derived profiles for a wide variety of proprietary products, which can be viewed free of charge on the Green Book Live website.

Both of these tools use an “ecopoints” scale which allows quick and easy comparison of products based on a common LCA methodology. They are ideal for designers and specifiers seeking to reduce the impact of projects without getting involved in calculations themselves.

BRE also produces software called Envest II which quantifies the full range of environmental impacts for a building based on LCA and contains a customisable estimating function to provide whole-life costs for projects. This tool is ideal for use at the design stage to calculate an LCA quickly in order to get to grips with the potential impacts and cost of a build.

General design advice

Despite the advantages of LCA, not every business will choose to use it, so here are some general guidelines to help to reduce the environmental impact of your build:

• Designing for long-life adaptability (such as using load-bearing external walls and reconfigurable partition walls) and universal access will avoid the need for big alteration work the Lifetime Homes standard can help here.
• Avoiding redundant structure and other features that add nothing to the building’s functionality will reduce overall material use.
• Consulting the Green Guide to Specification will allow you to weigh up the environmental impacts of your prospective build types.
• Using recycled aggregate and reclaimed masonry will reduce the embodied energy of your construction materials.
• Using locally sourced materials, including materials salvaged on site, will help to cut transport impacts.
• On site, aim to recycle as much waste as possible and sort as you go by separating timber, masonry and other waste into separate skips. Specifying standard sizes can help to avoid excessive offcuts.
• Floor coverings can have a higher impact than any other materials as they are replaced relatively frequently, so they offer a good route to reducing a build’s environmental impact.
• Using durable, low-maintenance and self-cleaning materials can help to avoid the need for regular maintenance work.
• Ensuring that materials can be easily separated when the building reaches the end of its life will help their reclamation and reuse.

Overall, life-cycle assessment can play a valuable role in reducing a project’s environmental impacts and can give businesses a clear grasp of where and how to improve their sustainability credentials. The current climate of legislative action suggests that those who embrace such measures will find themselves significantly ahead of the game as we move towards a sustainable, low-carbon future.