Add to ORKGAn overall objective of energy efficiency in the built environment is to improve building and systems performances in terms of durability, comfort and economics. In order to predict, improve and meet a certain set of performance requirements related to the indoor climate of buildings and the associated energy demand, numerical simulation tools are indispensable. In this paper we consider two types of numerical simulation tools: Finite Element Method (FEM) and Building Energy Simulation (BES). A well known benchmark case for BES, the so-called BESTEST, is used to verify Comsol (FEM) 3D simulation results. It is concluded that one of the main benefits of FEM-BES modeling exchange is the possibility to simulate building energy performances wit...