The topic of bachelor´s thesis is approximated of thermal bridges. The basic thermal bridges ( corners, wall and roof connection, window jamb, ground slab junction) are simulated in two dimensional, stationary heat field using finite element method. Used program are desribed in short, also their main features. the pros and cons. Each simulated building detail is subsequently modified in order to linear thermal transmittance was as small as possible, a negative number. After collected each value of linear thermal transmittance is compared influence to heat loss by heat transfer. From the specific building geometry is in two ways calculated heat loss by heat transfer. In first case is calculated by STN EN 12 831, which includes calculating heat losses caused by linear thermal transmittances with additional charge. In second case, heat loss is calulated by heat transfer counting linear thermal transmittance and lenght of detail. There are used the best and the worst values of linear thermal transmittance. We have found that linear thermal transmittance which are well designed from the thermal point of view are almost not a thermal bridges and they should not be counted in overall heat loss by heat transfer.