A large multifamily complex of about 21'000 square meters (three buildings) was recently raised in the suburb of Geneva (Switzerland) and was certified Minergie®, a Swiss quality label. From the preliminary draft to the buildings construction, a close attention has been given to the energy concept by an interdisciplinary group made up of architects and engineers. This outstanding realization is actually under monitoring by the Energy centre of the University of Geneva (CUEPE) for a four years period. This paper presents some aspects of the project of realizing a large-scale Minergie building. Annual gas consumption per unit of gross heated floor was measured as 228 MJ/m2 for the first year, more than the predicted value of 92 MJ/m2, and will probably lower to 191 MJ/m2 for the second year. Although higher than the designed value, the performance of these buildings remains excellent compared to the usual measured values for recent buildings (350-400 MJ/m2), especially considering their large scale and residential nature. The design, realization and exploitation stages are currently under investigation in order to better understand the difference between designed and measured value.