The aim of the work is to analyze the building system of cross-laminated timber - CLT. The introduction deals with the basic characteristics of this system, such as history, production technology and an overview of the possibilities of constructing the system from the CLT panels. From this construction system it is possible to build family houses as well as apartment buildings. The core of the work is focused on the overview of connection details and the calculation of the basic thermal parameters of the characteristic structures of the structure - the cladding, ceiling and roof cladding.