We present an ongoing project where five identical experimental constructions with different composite building materials of external walls have been created (the indoor area 9 m2, the height of ceiling 3 m). All external wall constructions (U=0.16 W/(m2K)) have ventilated façades. Five different insulated materials are used: aerated concrete, ceramic, lightweight concrete, wooden constructions, and an innovative composite building material developed in the course of the project. To provide identical thermal performance of the constructions, infrared (EN 13187) and fan pressurization (EN 13829) tests will be performed. 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 (EN 15251), while keeping the HVAC system solution identical. To analyze the energy efficiency parameters and the quality of indoor environment, outdoor parameters, indoor air quality, and thermal environment parameters will be measured. The monitoring will continue for a whole year, in order to evaluate and analyze the influence of different outdoor parameters in the natural meteorological conditions for Riga, Latvia, which correspond to cold maritime climate. The collected energy efficiency data and the quality of indoor environment parameters will be used to verify a corresponding multi-physical model. The project aim is, by using a multi-physical modelling method, to forecast the influence of different building envelope materials on energy efficiency and the quality of indoor environment.