How green is your specification?

The Government and the market are leading the construction industry down an increasingly green path. Designers and contractors are expected to be able to produce low-energy buildings using environmentally responsible construction processes. Materials producers are expected to use less energy in production, and the Building Regulations are soon to be toughened up on issues like insulation.

But it is difficult to make a difference on site. For instance: is it environmentally sound to use timber from fast-growing fir trees even though it has been transported thousands of miles from Scandanavia? It may be better to use timber from Scotland, reducing the impact of transport.

The lifetime or replacement factor for a product can also have a significant effect on a building's lifetime environmental impact. As if this was not difficult enough to calculate, decisions on one element will have implications for the quantities of materials used elsewhere in the design.

So BRE, in conjunction with DETR, has developed Envest. This is a software tool that helps specifiers determine the environmental impact of their construction decisions.

Total environmental impact

Based on life cycle costing, Envest is the first UK software that is able to estimate lifecycle environmental impacts of buildings at the early design stage. This version is designed for office buildings, and considers the environmental impacts of both the materials used during construction, and the energy and resources consumed over the building's life.

Using minimal data entered through simple input screens, Envest allows specifiers instantly to identify those aspects of the building that have the greatest influence on its overall impact.

And you will not need a degree in physics to understand it. All environmental impacts are measured using a single points scale called Ecopoints, allowing designers to make direct comparisons between different designs and specifications. One hundred Ecopoints are equivalent to the environmental impact of the average UK citizen in one year.

The software is easy to use; its simplicity belies the wealth of researched data - on materials, operational use, impacts and weightings - that underpin its calculations. This BRE tool is informed by over four years of research into the environmental impacts of different materials in association with the UK building materials industry.

User-confidence is vital

Life cycle assessment for construction materials and buildings provides information on the environmental impacts arising from the entire life cycle of a building: the extraction of the materials and their production; the various phases of construction; the building's use and maintenance, and its demolition and disposal. Life cycle assessment is a powerful tool, but if material users are to be confident in using the data to make comparisons between different products, it is important that all information is collected according to the same rules. BRE has achieved this through the development of an industry agreed "level playing field" method for life cycle analysis called environmental profile. These can be examined in more detail at www.bre.co.uk/envprofiles.

The environmental impact of a building is greatly affected by the length of its useful life - the same is true for its individual elements. Envest uses built-in values for the life of building elements and has a default value for the expected life of the whole building. The user can also enter their estimate of the building's expected life.

Specifiers can use Envest to make comparisons between different buildings and specifications, and graphically illustrate the environmental credentials of various design options to clients.