This article proposes a methodology to assess building behaviour, whilst taking its life cycle into account. Understanding of the system can be obtained by combining well-known energy consumption calculation engines (TRNSYS) with co-simulation processes defined using Specification and Description Language (SDL). In this instance, to find the best comfort, energy and cost scenarios for energy rehabilitation, Co-simulation is conducted in two phases: the best scenes of passive systems are found, those presented as a priority; and, the active systems are made with â€˜brute force analysisâ€™. The article provides the results for a case study: a single-family home built between 1991 and 2007 and located in Mediterranean climate zone. The methodology provides a set of passive energy efficiency measures, to improve until two scales in the building energy labelling system. Using the methodology and the proposed model has enabled us to dramatically reduce the run time until 75% and therefore.