The diploma thesis deals with the economic evaluation of an investment in an office building with different technical and environmental standards. The aim is to assess whether, from the investor’s perspective, it is more advantageous to implement a premium Class A building compared to a more cost-efficient Class B+ variant. The theoretical part focuses on the principles of sustainability in real estate development, financing options for office projects, international certification systems (in particular BREEAM and LEED) and the related legislative requirements. The practical part, designed as a case study of the D5 office building in the Nová Zbrojovka area, compares both variants in terms of construction costs, CAPEX, OPEX, rent levels, cash flows, as well as banking requirements and the ESG strategy of CPI Property Group. The results show that, despite higher investment costs, Variant A achieves a higher return and fits better into CPI’s portfolio. The main identified risk is a potentially insufficient demand for the premium office segment.