The building sector represents a significant proportion of the world’s energy consumption and greenhouse gas emissions. One of the possible contributions to reducing this problem is to improve the energy performance of buildings by acting on their envelope and systems. Consequently, the aim of this work is to develop an experimental and numerical methods for characterizing the thermal performance of a concrete masonry hollow wall, in order to propose a new configuration that can be used to improve its thermal performance. First, this study focuses on the thermal performance of different wall configurations. Then, each case studied at wall scale, was modeled, and simulated in 3D using COMSOL Multiphysics ® software under the same conditions, properties and dimensions as the one tested experimentally. Finally, this analysis was applied to a real building in Lebanon, consisting of hollow concrete masonry walls, to study its energy and thermal requirements. The conclusions showed that the numerical and experimental results proposed for the hollow masonry block wall confirm a good match. This validates the value of this method in the construction sector by proposing new methods for improving its thermal and energy performance.