In the present experimental work, two identical real field experimental setups (with dry soil and wet soil) of ground-air heat exchanger (GAHE) have been developed in order to evaluate the influence of change in inlet air temperature, airflow velocity, diameter of pipe and soil moisture content on the thermal performance of GAHE system. Influence of these parameters on the required pipe length to produce a specified drop in air temperature has also been investigated. Results reveal that the drop in air temperature achieved from GAHE having dry soil is 11.2 degrees C at 60 m pipe length, whereas, for GAHE with wet soil having 20% moisture, the same amount of drop in air temperature is obtained at a pipe length of 28 m only. Moreover, upon increasing the airflow velocity from 2 m/s to 10 m/s, cooling capacity of GAHE with dry soil, wet soil with 5% moisture and wet soil with 20% moisture increases by 122%, 185% and 220%, respectively, after 6 h of operation, but the effectiveness of the GAHE system with dry soil, wet soil with 5% moisture and wet soil with 20% moisture decreases by 55.4%, 42.5% and 36.2%, respectively. (C) 2019 Elsevier Ltd. All rights reserved.