International Conference on Sustainable Materials, Systems and Structures (SMSS 2019) Energy Efficient Building Design and Legislation 20-22 March 2019 – Rovinj, Croatia Page 83 MULTIDIMENSIONAL HYGROTHERMAL ANALYSIS OF COMPLEX BUILDING CONSTRUCTIONS Balázs Nagy (1) (1) Department of Construction Materials and Technologies, Faculty of Civil Engineering, Budapest University of Technology and Economics, Hungary Abstract In accordance with nowadays building energy performance requirements, building constructions developed significantly in the past few years due to new construction materials and building elements, because of the need for increased thermal insulation layers and the development of new building technology solutions. However thermal performance requirements are tightening, there are no moisture performance requirements connected to them, therefore in most cases, building construction design, if at all, only include simplified vapour transfer calculations. This paper presents a comparative analysis of multidimensional conjugated heat- and moisture transport numerical FEM simulations of modern building construction joints. For comparison reference, thermal simulations were made, neglecting the hygrothermal aspects. In the paper, besides the detailed wall section, a wall corner joint is presented, both built in 2D from complex building elements, such as insulation filled masonry blocks and were tested using different fillers (aerogel, expanded perlite, expanded polystyrene, mineral wool and PUR foam), respectively. The hygrothermal material properties of the insulation filled masonry blocks were measured in laboratory. The evaluation of the numerical simulation results shows that there are significant differences between thermal and hygrothermal approach and well insulated construction joints behave differently against heat and moisture using different thermal insulation fillers in the masonry blocks. Keywords: Thermal Insulation Filled Masonry, Heat and Moisture Transfer, Building Construction, Thermal Bridges, Moisture Bridges 1. INTRODUCTION In accordance with nowadays building energy performance requirements [1] building constructions developed significantly in the past few years. Material producers also started to develop new products to prepare for even tighter requirements in the near future [2], when nearly-zero energy buildings (NZEB) will be the standard to be built. To achieve significant reduction in the heat loss of the buildings, the demand is increased for particularly thermal