Buildings use almost 40% of all energy in Finland. New law about energy certifications come into effect 1.6.2013 and since then it has been the most important law behind energy certifications. The subject in this thesis is calculating energy efficiency in a detached house according to the Finnish Building Regulations (parts D3 and D5).

The purpose of the thesis was to draw up a spreadsheet with Excel and calculate the energy efficiency act. At first, the basics and output values of the example building has been presented. Energy efficiency has been calculated for electrical heating, district heating and geothermal heating. At the end, the results have been estimated.

In the results it can be seen that electrical heating is a bad solution. District heating and geothermal heating are better solutions.