The objective of the thesis is to improve the design of a typical single-family house in the area of Ljubljana to reduce operational energy for heating and cooling. Taking energy efficient measures in an early phase of planning is as requisite as following statutory demands for building design and sustainable design principles with passive solar architecture implementation and energy efficiency improvement of the building. Operational energy optimization was completed by using software tool BEopt for energy performance simulation. We are aware that building design measures have to be adapted appropriately to future climate change, therefore we presented the differences between individual building measures in 2010, 2020 and 2050 and evaluated adequacy of individual measure in comparison to the reference model. On this basis we designed a model with the combination of most energy efficient measures. In the thesis we chose a scenario with IPCC's A2 projection of climate change that is defined as medium-high emission scenario. Further, temperature and solar irradiation rise could be expected, which emphasizes the importance of building design measures as shading, window area decrease and the use of high thermal mass building materials to delay heat transfer. In conclusion, the most energy efficient measures are appropriate selection of heating system and improvement of building´s envelope thermal transmittance.