In the present study, the direct utilization of borehole as a heat sink for both residential and office building is investigated in Tabriz city. The effect of external wall insulation and windows glazing is studied in the form of four cases and the performance of the ground sink direct cooling system is investigated for these cases. The borehole design depth is calculated by analytical method. Both sample residential and office buildings are investigated. The borehole design depth depends on the quality of the building design and its heat emission. The results show that using double glazed windows, compared to single glazed windows reduces the borehole design depth by about 10 percent. Also the utilization of insulation in external walls and roof decreases the borehole design depth more than half compared to buildings without insulation. Finally, the potential of the ground sink direct cooling in sample residential and office buildings is investigated for four cases. The results show that by using ground sink direct cooling system, thermal comfort is satisfied in almost all of the cooling hours in both sample residential and office buildings.