This study investigated the cooling effect of an Earth Water-Air Heat Exchanger (EWAHE) device for ventilation applications. To address the lack of data on EWAHE performance in moderate climates, we measured temperature parameters (inlet-outlet, indoor-outdoor, water, and soil) continuously for three days. Air temperatures, air flowrate, light intensity are measured using a multi-channel data logger with several sensors. Results showed that the EWAHE effectively reduced indoor air temperature by an average of 7.5°C with a maximum reduction of 9.3°C, offering a promising passive cooling solution for buildings. The primary limitation of this study is that it requires open space around the building to place the device, so this method is inappropriate for building in a dense urban area. Future studies could investigate the association between ground-water cooling effect and natural ventilation without using energy for air circulation.