Building a greener future

Construction is essential to man's quality of life and well being. It is a major economic sector (17% of GDP) and employer (14 million people). However, construction also has a massive impact on the environment, partly as a result of the materials that are consumed. Six tonnes per person of materials are consumed annually for construction activity.

Four materials comprise over 99% of construction mass - aggregates (sand, gravel and crushed rock), cement (and hence concrete), brick (and clay products) and wood (which is mostly imported).

Energy used to manufacture and transport building materials represents about 10% of national totals. This is small compared to the 50% used to operate buildings or 22% consumed by personal transport.

Most of the mineral resources used are physically abundant. The real problem is one of access. Twenty per cent of our land area is developed and we greatly value the green spaces between and around our urban areas.

Wood is a renewable resource which locks up carbon dioxide during its constructed life. However, in the UK, we import over 90% of the wood used in buildings from Northern Europe and North America and Canada. There is some contention over whether this timber is being managed sustainably.



Wastes from construction and materials producers jointly represent about 30% of the UK total. Approximately 50% of waste from demolition is recycled, more for the high value materials such as metals.

Masonry and concrete materials are often only recycled to low grade applications and sometimes just to avoid landfill costs. "Design for deconstruction", such as the appropriate use of soft lime mortars to allow for reuse of bricks, is to be encouraged.

The environmental impact of materials is very diverse and all materials producers are keen to emphasise the best environmental attributes of their materials. Hence, it is a complex matter to assess the impact of their materials objectively.

Some of the main problems are:

l Deciding what issues to consider.

l Considering the materials in context. A small mass of relatively high impact materials may perform the same function as a high mass of low impact materials. It is not obvious which of these alternatives will give the lowest total impact.

l Comparing reusable or recyclable products with ones that are not - and assessing the potential for recycling at the end of the materials' life.

l Taking account of the durability, life and maintenance implications.

l Judging the relative importance of different impacts.



Life cycle assessment (LCA) is generally considered to be the most comprehensive method of dealing with these issues. It considers a defined range of environmental impacts from a defined function over a defined lifetime. However, there are many different ways of undertaking an LCA and the process is therefore vulnerable to the influence of vested interests on the outcome of such studies.

To meet this challenge, the Building Research Establishment worked with DETR (and a large number of materials producers and their trade bodies) to develop a robust set of objective guidelines for LCA of building materials and components. The result has been a publication entitled "Environmental Profiles of Construction Materials, Components and Buildings" and a database of "level playing field" LCA information, available on the Internet.

The sketch design stage is the point at which the most significant materials specification choices are made. A line on a sketch plan denotes between 0.5t and 2.0t of materials per m2 of the drawn object. To inform decisions at this stage, information must be presented for unit area of each element e.g. 1m2 of wall, floor, roof, ceiling etc.

The Green Guide to Specification uses this approach and scores different specifications with A, B, C ratings (A being good). The guide is available in versions for office and domestic buildings and use of A and B rated elements from the book provides credits in the BREEAM assessment for offices and the new Ecohomes Award.

Information about materials alone is obviously not enough. The designer must also take account of the operational performance of the building for energy and water consumption and wastes generated. An initial design tool, Envest, has been developed to explore the major early design trade-offs, for example between the impact of insulation and the energy saved by insulating.

To make the consideration of environmental matters easier, alongside the many other attributes to be considered in materials selection, the complex information must be distilled down to a robust but simple form. This has been achieved with Ecopoints, a single life cycle score system. The score is based on LCA with a consensus approach to determining the relative importance of different issues. Ecopoints are used to show the relative impact of different design choices in the Envest tool. The tool is very simple and results are achieved through the choice of different menu options, as shown in the five steps illustrated in the table (opposite page top right).

It is important not to confuse life cycle assessment (LCA) with whole life costing (WLC). The former has been designed to assess environmental impacts of choosing certain design options and the latter to assess financial costs of choosing certain design options.

The joint LCA/WLC approach is very useful and has been applied in a number of high profile developments. One of these is the new Wessex Water HQ building in Bath, (see M4I demonstration projects pages 20 to 25) which was built with the intention of providing a state- of-the-art building in terms of sustainable design. LCA, in the form of Envest-derived Ecopoints, was used by Bennetts Associates to determine the choice of overall structure, frame and roof covering for the building, working alongside cost consultants.



Even at the later stages of the design, a joint LCA/WLC approach was useful in determining where to focus the energies of the design team most productively. Using Ecopoints it was evident that, since typical flooring under consideration had three times the impact of the typical ceiling finishes, it was most appropriate to concentrate on the floor finishes. Further to influencing the choice of product type, the Ecopoint score was ultimately used to guide the design team towards identifying suppliers who could offer the lowest environmental impact.

As awareness grows within the construction industry about the types of tools available and the benefits from the environmental savings they can offer, it is likely that buildings designed using a life cycle approach will become the new standard.

Comparing results from a wide range of viable buildings provides benchmarks of performance that clients can use to specify their environmental aspirations, or assess their property portfolio for risk from environmentally damaging buildings.

l While this article demonstrates the potential of LCA, it should also be clear that the subject as a whole is still at the stage of development and its application to building materials and buildings is no exception. It is important to present the information in such a way that it cannot be used out of context by building professionals and their clients. With sensitive use, LCA will provide a valuable tool in helping towards the goal of sustainable construction.

Environmental profiles, Ecopoints and Envest have all been produced with the support of DETR.

For further information on the tools and issues discussed in this article, visit the BRE Website on:www.bre.co.uk/sustainable/index.html.

Or contact the Centre for Sustainable Construction on: 01923 664307 or csc@bre.co.uk



BOXTEXT: INBRIEF



l All materials' producers are keen to emphasise the environmental attributes of their product. But how can firms assess the impact of materials objectively?



l Life Cycle Assessment (LCA) is considered to be the most comprehensive method of assessing the environmental impact of materials, as well as The Green Guide to Specification. Envest and Ecopoints are two environmental design tools.