Computer simulation and field studies were conducted to investigate the implementation of natural cooling strategies in existing apartment buildings in Athens; the most typical urban domestic building type of Greece. Thermal performance analysis and airflow modelling in a specific apartment were conducted for the summer period using dynamic building energy simulation tools. The indoor thermal comfort was evaluated with reference to the adaptive thermal comfort theory. Changes to the fenestration and the utilisation of a light shaft, assist the natural cooling of the building and improve the previous single-sided ventilation strategy. Results indicate indoor air quality in the spaces being significantly enhanced, whilst the percentage comfort hours were increased, suggesting a significant reduction of the buildings’ cooling demand.