The thesis describes and analyses the three typical single family houses, which were built in
1967, 1999 and 2015. A calculated energy performance certificate was done for all three
houses. Measures were also proposed for the older two houses to increase energy
efficiency. It describes issues focusing on legislation governing the areas related to energy
issues and energy certificates with an emphasis on Slovenia and partly on the European
Union. The computer programs TEDI and TOST were used to develop the Thesis. TEDI
allows us to calculate the heat transfer coefficient of construction and TOST is used to
calculate energy balance in accordance to Pravilnik o učinkoviti rabi energije v stavbah
taking into account SIST EN ISO 13790 and TSG-1-004-2010. The main purpose of this
study was to calculate the energy efficiency of buildings and to compare the obtained results.
Analyses showed that the new house (2015) is very energy effecient in comparison with
older houses. It spends forty times less heating energy per square meter of usable area as
the oldest house (1967), and ten times less than the house built in 1999. It turns out that
alredy minimal thermal insulation greatly reduces heat demand of the house, and that we
have witnessed significat progress in use of insulation materials in last fifteen years.