The diploma thesis is based on the existing building of a single family house in Izlake, which was built in the early 1980s. Like most buildings constructed at that time, it needs complete renovation and at the same time a renewal of the thermal envelope in order to be more energy efficient. The diploma thesis presents and analyses the thermal envelope of the existing and renovated condition of the building using the Ubakus software tool. Thermal bridges were identified using thermal imagery, while their linear thermal transmittance was determined by the standard SIST EN ISO 14683. Based on these data, the energy efficiency of the existing condition was calculated using the KI Energy program. This is followed by a proposal for the restoration of the existing condition, which was made on the basis of the "Rules on Efficient Use of Energy in Buildings (PURES)"  and the requirements for obtaining an Eco Fund grant. The complete renovation is divided into four parts of the renovation: facade, roof, interstorey structure and exterior joinery. This demonstrates the transparency of the energy renovation of each part of the renovation. The obtained results show that the total heat energy savings for the whole renovation is 21641 kWh/year. Regarding the partial renovation of the thermal envelopment, the most efficient is the replacement of the exterior joinery with savings of 7381 KWh/year, followed by the facade renovation with savings of 6248 kWh/year, the restoration of the interstorey structure with savings of 4201 kWh/year and the renovation of the roof with savings of 868 kWh/year. Finally, the economics of each part of the renovation is made according to the estimate of the company Zagrad d. o. o. and the Eco Fund grant, given the cost of heating with a heat pump and a fuel oil stove. Since heating with a fuel oil stove is 2.53 times more expensive than heating with a heat pump, it is reasonable to choose a heating system with a heat pump. As a result, the time to cover the investment costs is significantly longer, given the cost savings for heating.