It is acknowledged that people spend almost 90 percent of their time in indoor spaces. Therefore, achieving a comfortable indoor environment that encourages productivity is crucial, particularly in office buildings. This paper investigates the design and performance of a modern office building in London characterized by fully glazed facades of open plan office spaces with no natural ventilation. The purpose of the research is to investigate the correlations between the control of direct solar radiation access and the effect on occupants’ thermal comfort in the summer followed by assessing the potential effect of the application of passive solar shading on thermal comfort levels in the office spaces. The research methodology involves a survey questionnaire undertaken with employees of the office building, followed by dynamic thermal modelling of the building using Integrated Environmental Solutions (IES) software. The questionnaire has been designed to understand occupants’ experiences within their office spaces and their strategies to improve the indoor environment. Furthermore, IES modelling and simulation provide in depth understanding of the building thermal performance and investigating the solar shading strategies. Overall, 66 questionnaire forms were completed where preliminary results demonstrated that most employees relied heavily on secondary cooling and heating systems to adjust the indoor air temperature for more satisfactory thermal comfort levels in their office spaces. The building modelling and simulation is used to quantify the direct solar radiation accessing the office space, the risks of overheating and the potential impact of solar control on occupants’ indoor comfort. The findings from this study demonstrate the potentially high hours of discomfort in the summer within the office spaces mainly due to the lack of control of direct solar access through the extensive area of glazed facades. In order to maintain the thermal environment within the comfort level threshold in the warmer seasons a solar shading strategy should be considered.