Greenhouse gases and building lifetimes

The aim of the article is to study the impact of a buildingʹs lifetime on greenhouse gas emissions. The influence of the lifetime of a dwelling with its performance levels maintained is studied according to the technical solutions chosen. The emissions due to heating and cooling are neutralized for the occupancy phase and only those of the buildingʹs embodied energy, demolition and maintenance phases are taken into consideration. In a first step, the evolution of the emissions with time is simulated on the basis of lifetime hypotheses for the technical solutions. This step enables the impacts of these phases to be compared with that of the occupancy phase, thus revealing their relative importance depending on the components of the dwelling. In a second step, since the lifetimes of the solutions are uncertain and difficult to predict given that future political, cultural and energy price evolutions are unknown, the hypotheses used in the first step are called into question and greenhouse gas emissions are evaluated according to variable lifetimes. Finally solutions with equivalent impacts are found. The results show that it is not only the choice of a technical solution that determines performance in terms of greenhouse gas emissions but that the lifetime has a very significant effect which must also be taken into account. Impact evaluations could evolve in the light of these results, as could the tools based on life cycle analyses.