This research investigates the potential of Electrochromic (EC) glazing as a significant innovation in solar control glass, enhancing both indoor environmental comfort and energy efficiency for sustainable construction. The study's objective is to conduct an empirical evaluation of the effects on visual and thermal comfort offered by Double EC glazing windows. This adjustable EC window is tested in the challenging conditions of Saudi Arabia's hot desert climate. A detailed scale model of a south-facing office was constructed, featuring high insulation. It facilitates the measurement of key parameters such as overall heat transfer, heat flux, and daylight distribution across different transmittance states during summer solstice. The results revealed that the test EC system in opaque state, was effective in reducing heat loss from the interior, but eliminate the minimum daylighting quantity to enter the space. While the intermediate state could achieve the recommended of illuminance value and reduce heat gain. Thus, the EC control strategy and balanced solution based on the external environment require further investigation in particular at hot desert climate.