Abstract: In this study, evaporative cooling barn was designed, constructed and tested using two varieties of sweet potato. The mean dry bulb temperature and relative humidity of the inside and outside air stream were 25°C and 90% and 31.5°C and 67.5%, respectively. The systems cooling efficiency was determined to be 127%. A test on the evaporative cooling barn using 18 mini sacks, each containing 14 tuberous roots with four replications for 12 weeks, revealed that moisture loss from the two varieties are approximately the same (13%). The moisture content of the root tubers decreased linearly from 68 to 59% and 60 to 52% (wb) over a storage time for TIS 2 and Ukerewe, respectively. Percentage weight loss increased linearly from 0 to 11.4 and 0 to 11.9% for TIS 2 and Ukerewe, respectively. The percentage wholesomeness decreased linearly with storage time from 100 to 76% and 100 to 60% for TIS 2 and Ukerewe, respectively. Percentage weevil damage increased non-linearly with storage time and started 6 and 10 weeks in storage for Ukerewe and TIS 2, respectively; percentage sprouting increased non-linearly with storage time and started 4 and 6 weeks for TIS 2 and Ukerewe, respectively. Percentage shrinkage increased linearly with increasing storage time from 0 to 3.6% and 0 to 4.6% for TIS 2 and Ukerewe, respectively. Percentage decay increased linearly with increasing storage time from 0 to 29% and 0 to 76% for TIS 2 and Ukerewe, respectively.