Impact of the lifespan of building external walls on greenhouse gas index

The paper focuses on the assessment of greenhouse gas emissions produced by the walls of buildings according to their lifespan. These assessments take account of the construction, maintenance and end of life. The contribution of the utilization phase must be equivalent for all technical solutions for a given usage function. In the first part of the paper, the methodology is described by (1) considering a unit area of wall (i.e. 1 square metre), (2) determining a long service life, (3) choosing technical solutions in agreement with the specifications, (4) establishing the lifespan of each technical solution according to experts, (5) finding the corresponding greenhouse gas index from an appropriate database, and finally (6) modelling the evolution of these indicators with time. Several technical solutions (concrete, brick, stone, wood, aerated concrete) are considered and lifespans range from a few years to centuries. The results of this analysis suggest and quantify the important impact of lifespan on greenhouse gas emission indicators. For example, the best technical solution for a short lifetime can be the worst on a longer duration and vice versa. In the second part, since the lifespan of a product is very difficult to determine objectively, it is considered as a variable. The numerical results presented point out the need to revisit the current life cycle tools.