Turkey has undergone inadequate development during a process of rapid urbanization and growth since the 1950s, parallel to reduced construction costs for residential buildings. This has contributed to household energy consumption in Turkey growing to twice the global average, and twice the averages of European Union member states. In response, the Energy Efficiency Law and other energy performance regulations were enacted in 2007. As a part of "Assessing the Inventory for Renewable Energy Utilization in Existing Residential Buildings and Setting Up Local Design Parameters," supported by the Yildiz Technical University Scientific Research Projects Coordination Department, Istanbul's Beykoz District was chosen as the case area. Using solar energy for heating purposes is popular in Beykoz for a number of reasons, including the prevalence of mostly detached buildings and abundant green space, as well as less building density and fewer stories, compared to the city center. Four buildings were studied in order to identify improvements that would allow for a reduction in cooling and heating loads in existing residential buildings in the context of building envelopes. Research of the four existing residential buildings executes similar results. Results of the study of a multi-family residential building in the neighborhood of Kanlica is presented. Determined by the calculation of cooling-heating loads and carbon emissions, improvements designed to efficiently utilize solar energy where the building envelope permits are identified. These improvements address window space, eaves, and characteristics, as well as exterior wall insulation thickness, draft prevention, shading, landscaping features, and control of solar energy. Average monthly and annual heating-cooling requirements were calculated using IESVE simulation software. The improvements yielded a 72% drop in annual heating energy consumption and a 24% drop in annual cooling energy consumption, resulting in an average drop of 62% in CO2 emissions.