The thesis describes an analysis of the effects of linear transmission losses of the most common thermal bridges that occur in a typical single-family house. Numerical method for calculating the heat flow using the UcanPsi software in combination with SIST EN ISO 10211 and SIST EN ISO 13370 was used to determine the influence of thermal bridges. Part of analysis and final calculation is based on standard SIST EN ISO 14683. Junction between window and external wall, balcony slab edge and joint between ground floor and external wall were used as typical representatives of the linear thermal bridges. As a result of the thesis there are two spreadsheets attached that might help users to quickly assess the influence of the thermal bridge in relation to the length of the balcony with correlation to the amount of glazing. Spreadsheets represent values of the transmission heat transfer coefficient (HT) and percentage of heat loss by uncontrolled linear thermal bridges (DTM).