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Abstract. The aim of this study was to compare and analyze the air temperature and humidity distribution and energy consumption using air circulation fans in single-span greenhouses in Cheongnam-myeon, Cheongyang-gun, and Chungcheongnam-do, Korea. Cherry tomatoes were cultivated in the greenhouses and each greenhouse had a ridge height of 3.2 m, width of 6 m, and length of 95 m. The heating system used comprised of a hot-water boiler and six fan coil units , four of which were installed at the bottom with vinyl ducts and two were installed at a height of 2.0 m. A total of 18 air circulation fans (impeller diameter : 230 mm) were bilaterally arranged in two rows in the experimental greenhouse. The sensors for measuring air temperature and humidity were located at a quarter and three quarters of a length (95 m) and height of 0.8 m, 1.8 m, respectively. To calculate energy consumption in the greenhouses, water temperature and volume at the inlet and outlet of a water pump were measured. Form February 3 to March 23, temperature, humidity and energy consumption were measured during heating hours (18:00-7:00). In a greenhouse without fans, the average differences in temperature and humidity was 0.75°C, 2.31%, respectively. When fans were operated, the corresponding differences were 0.42°C, 1.8%. The standard deviation of temperature and humidity between measuring points in the greenhouse with fans was lower than that in the greenhouse without fans. The total energy consumption in the greenhouse with fans (4,009 kWh) was 14.2% less than that in the greenhouse without fans (4,673 kWh). Therefore, air circulation facilitates uniform temperature and humidity and reduces energy consumption for heating.