The aim of this bachelor thesis is to define the elements of sustainability in construction and to analyze the level of implementation of ESG (Environmental, Social, Governance) principles on selected construction projects in the Czech Republic. The theoretical part maps the historical development of sustainability, the transition to whole-life carbon (WLC – Whole Life Carbon) assessment, the application of the circular economy, and the impact of new European legislation including the EU Taxonomy. In the practical part, an original "ESG Maturity model" is applied to five case studies selected based on a contrasting approach (from a standard utilitarian public procurement contract to a premium certified commercial development). The results of the comparative analysis prove the central thesis that the overall level of sustainability and project maturity is dominantly influenced by the investor typology and their requirement for independent certification. While certified projects achieve a highly balanced profile across all pillars, standard commercial and public construction tendered at the lowest price experiences fundamental deformations of the ESG profile, mainly due to the absence of exact carbon footprint data and the non-use of circularity principles.