The publication presents an ongoing project which aims, by using multi-physical modelling method, to forecast the influence of different building envelope materials on the energy efficiency and the indoor air quality (IAQ). In this project, five identical experimental constructions with different composite building materials of external walls will be created (the indoor area 9 m2, the height of ceiling 3 m). All external wall constructions (U=0.16 W/(m2K)) will have ventilated façades. Five different insulated materials will be used: aerated concrete, ceramic, lightweight construction, wooden constructions, and an innovative composite building material developed in the course of the project. In all the experimental constructions it is planned to ensure air exchange of 0.6 h-1 and indoor air temperature corresponding to category A (CR 1752:2002). The collected energy efficiency and IAQ parameters will be used to verify corresponding multi-physical models. The monitoring will continue for a whole year, to evaluate and analyze the influence of different outdoor parameters in the natural meteorological conditions for Riga, Latvia, that correspond to a cold maritime climate.