Envelope insulation improves indoor thermal comfort, reduces building energy use, and protects against climate change through reduced CO2 emissions. By 2050, with the projected mean annual global temperature expected to rise by 2 to 3 °C, naturally ventilated buildings in hot countries will likely experience increased thermal discomfort. This discomfort may prompt the installation of air conditioning units, leading to higher electricity demand and further emissions growth. This research uses energy simulations using DesignBuilder to study thermal discomfort in a typical case of social housing units in Egypt that currently lack air conditioning based on the ASHRAE 55 adaptive comfort model. The validated simulation model uses current and future weather for three different climate zones in Egypt (Cairo, Alexandria, and Aswan) and different envelope compositions to compare discomfort hours within different zones, given their expected occupancy schedule. While previous studies have examined the impact of building envelope insulation on thermal comfort using whole-building simulations, this research explicitly analyzes occupancy schedules and comfort in different spaces, such as dining and reception areas versus bedrooms. This novel approach highlights the need to investigate potential retrofits using space-by-space to improve thermal comfort in each area. The results showed that insulation does not improve thermal comfort during the day in zones without cooling systems. However, thermal insulation proved beneficial for zones occupied at night by reducing discomfort caused by heat loss. This suggests that zone-specific retrofits should be considered to improve thermal comfort for each zone while ensuring optimal space utilization.