The present paper gives an overview of a French national project on building performance. Named COMEPOS, started in 2013, it focuses on « Positive Energy » detached houses. It consists in the design, construction, operation and evaluation of 20 inhabited and innovative houses. This collaborative project includes constructors, industrial and academic partners, the latter involved both in the monitoring and the use of building performance simulation at different stages of the building's life. The paper offers an overview of how simulation technics can be used, in coordination with measurements, concerning points like the optimization of the design, performance evaluation, fault detection, but also improving simulation of real-life situations, for example by improving the knowledge about the impact of occupants' behaviour.