The state of the art experiments to investigate the hygrothermal performance of the whole constructions are often defined for one-dimensional transport processes only and typically executed by using the guarded hot-box / cold-box setup. The guard function is supposed to minimize the influence of the energy fluxes through the adjacent constructions enveloping the air-conditioned sides. However, measuring and testing the tall or complex geometric thermal bridge constructions are rarely done and remain a challenge. Therefore an innovative climate chamber design will be established. It is designed to investigate the performance of multifunctional active façade systems, including the roof components and its constructive joints. One of the challenging tasks is the provision of the pre-defined stable boundary conditions. This is an immanent precondition for the calibration and validation of simulation models. Particular difficulties in this setup are the specimen dimensions of up to 4x7 meters and corner details of corresponding size. The specifics of the guard construction for the hot-box side, as well as details of equipment connections, joints and breakthroughs are illustrated and discussed. Approaches to prevent the unintended heat and moisture flows at the boundaries of the specimen are also debated.