Energy reduction is a crucial problem in building load management in Pakistan since residential energy use is mostly focused on providing thermal comfort. Under severe weather, windows, which are infamous for having weak thermal barriers, significantly increase energy losses. Phase change materials (PCM) and transparent insulation materials (TIM), which have high thermal inertia, might potentially reduce energy consumption when used in windows. In this work, three different window designs are compared and examined, and their impact on interior temperature is evaluated using ANSYS Fluent numerical simulations. The study’s conclusions highlight the fact that PCM-based windows show very little temperature change during melting, highlighting their significant potential to reduce energy use. Moreover, PCM efficiently absorbs over 90% of incident heat, highlighting its importance in advancing energy efficiency in Pakistan’s building industry.