Sustainable design, which aims to reduce energy consumption and mitigate climate change, is a primary concern of developing countries. Hence, it reduces CO2 emissions. Residential buildings in North Iraq account for approximately 69% of all electricity consumed. To mitigate this issue, this article investigates the design of a sustainable model by considering the local climate, building design occupant behaviour, and sociocultural needs in the region and their impact on energy use. This study used mixed research methods to develop a sustainable single-family house model in semi-arid climates, specifically Erbil (North Iraq), the process consisted of three phases. Phase One saw the collection of all data from analysed literature, observation, worship, case study simulations of the base, and an improved model. Phase Two defined the guidelines for creating sustainable model dwellings based on the main findings in Phase One. Phase Three created a prototype to evaluate the sustainable model, primarily focusing on meeting people’s design preferences while avoiding privacy concerns. In addition, DesignBuilder Software simulation was used to examine the impact of occupancy behaviour (based on local culture and traditions) on the building’s energy performance throughout two phases. In the first step, three occupancy profile types are compared with real-life study bills. These profiles were the base case, which came from an actual case; the statistical profile from surveys; and the international standard ASHRAE 90.1, which was used as the default. The second phase compared the base model with an improved model and developed a sustainable prototype that satisfies local climate and sociocultural needs. The result indicated that the standard occupant profile significantly differs from the actual bill by 40%, whereas the statistical profile and base case reduce the gap to 11% and 4%, respectively. The sustainable prototype model can enhance operative temperature by 4 °C and decrease total energy use by 50% compared to the base case model. Data also showed that occupants keep lights on even when rooms are unoccupied. Therefore, when designing sustainable dwellings, it is crucial to consider occupant behaviour and their sociocultural needs, as they have a significant impact on energy use as a result of their activity patterns and schedules. These factors should be considered in the local code.