Eco-design of buildings using thermal simulation and life cycle assessment

Energy efficient building are designed to minimize heating, cooling and lighting energy loads, so that attention is now paid on the energy consumption related to inhabitants (e.g. use of appliances) and life cycle issues: fabrication of materials, construction, maintenance, dismantling and waste treatment. In order to study these aspects, both in new construction and renovation projects, thermal simulation has been linked to life cycle assessment. Until now, such studies consider a conventional occupantsʹ behaviour, or use monitoring results to adapt the model. The approach proposed here complements life cycle assessment with a sensitivity study in order to account for the variability in real occupancy scenarios, but does not require monitoring results so that it can be performed during the design phase. Application of this method is illustrated by a case study regarding two attached passive houses built in France. The results show the essential influence of occupants on the performance, but varying the occupancy scenario does not modify the ranking between the compared alternatives. Checking the robustness of life cycle assessment results increases the relevance of this method as a design aid.