LCA: Building and the Ecosystem

Existing Approaches

The objective of the environmental optimization of a building during its life cycle cannot for the present be met because of a lack of specific knowledge as well as appropriate planning and decision structures. The generally admitted need for a comprehensive approach implies that the interest of the concerned professionals converge, which is not necessarily so. A first group is mainly interested in energy related problems. Knowing the consumption of operation energy, the (gray) energy embodied in materials, processes and the preparation of final energy itself, has been estimated with different methods. This approach has been enlarged by the extension to pollutants through emission coefficients of typical energy transformations and transport processes. The representatives of this group generally assume that the total primary energy consumption is a possible (and already existing) indicator for the environmental impact. The main objective lies in a rational utilization of natural resources and in an enhanced economical approach (through external costs).

A second group is mainly interested in human toxicological problems. The German "Baubiologie" is one of the tendencies, the international research community around Indoor Air Quality and Sick Building Syndrome another. The main objective is the creation of a healthy indoor climate, a largely anthropocentric point of view. A third group is mainly interested in the (in our case destructive) consequences of human activities on the environment. Its objective is to (re)create natural cycles and to integrate the building process into these cycles. These different approaches will probably continue for some time; there is no general unified theory in view All the approaches have produced methodologies and decision tools which have been applied or could be applied to the building processes with the aim of optimizing a building during its lifetime.

Most approaches and tools share the following assumptions:

• The building has to be considered as a whole.
• The building has to be considered during its lifetime.
• The energy and material flows have to be known.

  All the proposed tools establish a more or less explicit relation between causes and effects. The levels differ however: in the human-toxicological approach the choice of a building material is related to its effect on the user (e.g. allergies); in the eco-toxicological approach the production of building elements from the tropical forest, for example, is related to climatic changes. There are three categories of tools which will be analyzed and compared in more detail:

1. restrictions
   In the form of the choices of production processes with an implicit evaluation.
2. product declarations
   The establishment of the inventory of a product or process within the chosen system limits. There is no evaluation other than the choice of the system limit and the choice of the indicated component.
3. impact assessments
   On the basis of an inventory, causes and effects are identified and evaluated. The evaluation models can differ very much in width and depth.

   
   > References

   Kohler,N. : Energy Consumption and Pollution of Building Construction. Third International Congress on Building Energy Management. EPFL-Lausanne, 1987.

   Kohler,N.; Lützkendorf, Th.: Energie und Schadstoffbilanzen von Gebäuden Schlussbericht Forschungsprojekt BEW. EPFL. Lausanne .1991

   Kohler,N.et al : Energie und Stoffbilanzen von Gebäuden während ihrer Lebensdauer .Schlussbericht Forschungsprojekt BEW. Ifib - Universität Karlsruhe 1994