In this paper the thermal model given by Ghoshal and Tiwari has been validated by round-the-year experimental work at IIT Delhi, New Delhi (28 degrees 35'N, 77 degrees 12'E), India. The correlation coefficient and root-mean-square percentage deviation have been computed for each month for validation of the thermal model. The values are 0.99% and 4.24% for the greenhouse temperature with an earth-air heat exchanger (EAHE) in the month of January. Statistical analysis shows that there is fair agreement between predicted and experimental values. An effort has also been made to optimize the working hours of an EAHE to obtain maximum heating/cooling potential. The non-operational hours of an EAHE are 252 and 279 for February and March months, respectively. The maximum value of heating potential (11.55MJ) and cooling potential (18.87MJ) has been found during off sunshine (8 pm-8 am) hours and peak sunshine hours (8 am-8 pm), for a typical day in the month of January and June. (c) 2005 Elsevier Ltd. All rights reserved.