In the year 2012 the Finnish building energy regulations were tightened. In the new regulations thermal bridges have to be a part of the energy efficency calculations. The aim of this thesis was to calculate the linear thermal transmittance values for a house factory and compare the calculated values with the reference values of National Building Code of Finland. In addition it was examined how large impact of the calculated thermal bridge heat loss had compared to conductive heat loss in an example building.

The adjoining structures were modeled with Autocad software using the help of Finnish linear thermal transmittances accouting guide. Then, the calculated models were simulated with Comsol Multiphysics software. The linear thermal transmittance values were determined from the simulation results. The overall heat transfer coefficients were calculated with the instructions of the National Building Code of Finland, part C4.

In the study all the calculated thermal transmittance values were lower than the reference values. In particular, the floor joints calculated values were crearly below the reference value. The example building’s conductive heat loss was 60 percent lower compared to the reference values. The calculated thermal bridges were about 8 percent of the conductive heat loss. When calculated with reference values it was 18 percent, which tells a lot of the necessary of the new regulations. The calculations according to the new regulations give a good picture of the actual energy preformance of buldings.