Higher energy consumption, especially for heating, in high-rise buildings than conventional buildings, necessitates partially supplying thermal energy by solar water heaters (SWHs). Considering the very high solar radiation potential in Iran, this study used roof solar collectors to partially supply the heat required for domestic hot water (DHW) and heat the indoor space and a swimming pool in a 48-unit building in a cold climate (Shahrekord, Iran). Climatic data were extracted from Meteonorm 7.3, and technical, energy, environmental, and economic analyses were performed with the help of TSOL 2018 R(1). The one-year dynamic analysis was performed, considering all possible losses, and an auxiliary gas boiler (AGB) was also used. According to the results, considering the available roof area, 8.7% of the total required heat equivalent to 82814 kWh is supplied by SWHs with a unit cost of $0.022/kWh. The AGB supplied 867259 kWh/year, preventing CO2 emissions by 25.5 tons. This is the first study in this regard in Iran, and the authors hope that the results can be employed as a guideline for decision makers to extend the use of SWHs in Iran.