BRE IP1/09 PDF

INTRODUCTION

The concept of LCA (see Box 1) underpins The Green Guide to Specification through its use of the Environmental Profiles Methodology (see Box 2). To use LCA in The Green Guide (see Box 3), it has been necessary to develop information on the service lives of the materials and components represented in the guide's elemental specifications. This is because every time a material or component is replaced, LCA must measure the environmental impact of the new material or replacement component (as well as the disposal of the old one). This makes it important to define specifically the rules for life cycle scenarios when undertaking LCA.

To ensure accuracy and comparability, the rules cannot consider a quantity of material such as 300 bricks or a tonne of steel in isolation. This is because a construction material or product can only be defined in life cycle terms when considered in the context in which it is used, eg such as a built specification for a wall.

A wall, or any other type of building element, can be assigned a service life within an LCA scenario model. In a scenario, the LCA considers the function of the building element for a set amount of time (a study period). In order for the LCA to model an elemental specification over the study period, parts or all of the specification will commonly require maintenance (and/or intermediate replacements), and at the end of the life, or the study period, an allowance will be made for the specification to be dismantled and disposed of.

By using this approach, different materials can be compared on a like-for-like basis as groups of components that fulfil the same or similar functions. This means that important variables such as the mass of material required to fulfil a particular function are correctly accounted for. This is critical for an LCA because the material mass has a direct link to environmental impact.