This paper elaborates the formulation and application of an integral methodology for overall energy performance improvement of office buildings and demonstrates its application. The developed multi objective methodology is demonstrated on a reference office building located in a temperate climate zone with high annual temperature variations. The idea is to formulate a research based proposition in building science with a formulation of a general/integral methodology which could be applied widely in energy performance refurbishment of existing office buildings and help architects and engineers in the early-design stages of new projects. The goal was to formulate an optimized building envelope model using multi-criterion optimization methodology in order to determine efficient window to wall ratio (WWR) and window geometry (WG) in the function of indoor illumination quality, followed by the assessment of glazing parameters influence on the annual energy demand. The integral methodology for overall energy performance improvement of office buildings utilizes multi-criterion optimization method and highly detailed Building Information Modeling (BIM) programs and dynamic energy simulation engines. The developed coupled-integral methodology links together both building envelope construction optimization and user comfort. The methodology is both flexible and adaptable for application in various climatic conditions and for different construction types. (C) 2016 Elsevier Ltd. All rights reserved.