LCA: LCA for Buildings

Environmental Impact of Building Elements

Element decomposition:

The building is decomposed into cost-elements. Each cost element has a geometrical or other functional unit (1 m2 of exterior wall, one heat production plant etc.). All elements are formed of real or virtual layers. A layer can be building material with a certain thickness (e.g. the 12 cm thick insulation layer in a roof construction) or a spread out building material (e.g. 100 gr. of Copper per m2 of heated surface for the heating distribution system). Each layer has attributes like the type of material, the quantity, the life time, the disposal category etc.. Layers can be defined in a simple physical way for the purpose of a LCA. They can form a catalogue of elements. It is also possible to define layers as (more or less standardized) building specifications and to link the element description to the complete construction description of a building.

Transformation in Time

The description of the transformation process of a building can be divided in two parts:

• replacement model :the description of the physical transformation due to use, age climate etc..
• the description of the maintenance and refurbishment process

  replacement model :

  Maintenance operations are the difference of sum of the mass of replaced layers during element life cycle and the mass of the initial (new) construction. Replacement is automatic and can be expressed by an average maintenance coefficient for a specific element. Refurbishment is the periodic, automatic replacement of an element at the end of its life time. The fact that this process is not continuos, but periodic can be taken into account by a coefficient.

  description of maintenance and refurbishment:

  Partial model 1 (physical description) : Replacement is considered like new construction. This is not exact (additional deconstruction and waste is not considered).
  Partial model 2 (specification) : All maintenance and refurbishment process are related to the state of the element (after diagnosis). The construction operations are specified like new construction taking into account all operations like partial deconstruction, repair etc.

   

  
  > References

  REGENER - (Regional planning for the development of renewable energies).first interim report, June 1995, Ecole des Mines - Paris

  Kohler N. (1994) et al : Energie- und Stofflussbilanzen von Gebäuden während ihrer Lebensdauer. Schlussbericht des Forschungsprojektes des Bundesamt für Energiewirtschaft. Lausanne/Karlsruhe 1994