Effect of Greenhouse Cladding Materials and Thermal Screen Configuration on Heating Energy and Strawberry (Fragaria ananassa var. “Seolhyang”) Yield in Winter

Strawberry cultivation depends on environmental factors, making its cultivation in the greenhouse a challenge in the winter. This study investigated the most appropriate greenhouse cladding material and thermal screen configuration for strawberry production in the winter by considering greenhouse air temperature, relative humidity (RH, vapor pressure deficit (VPD, and solar radiation (SR). Two gothic greenhouses with different cladding materials and thermal screen configurations, namely, the single-layer greenhouse and double-layer greenhouse, were used for strawberry cultivation. The greenhouse microclimate was controlled by natural ventilation aided with circulating fans and boilers. Strawberries were planted on 5 greenhouse benches, 660 stands per greenhouse. Daily environmental parameters were recorded and processed into daytime and nighttime. The impacts of cladding material-thermal screen configurations on temperature, RH, VPD, and SR, and the subsequent effect on strawberry yield in both greenhouse systems, were evaluated. Comparing the environmental parameters recorded in the single-layer and double-layer greenhouse showed that VPD and SR were significantly different in the daytime, whereas RH and VPD were significantly different in the nighttime. The post hoc test further showed that RH, VPD, and SR in both greenhouses were significantly different. The significant difference in RH and VPD can be attributed to the inner layer of polyethene in the double-layer greenhouse, which sealed up the pores of the thermal screen, resulting in humidity buildup, causing a lower VPD than in the single-layer greenhouse. The single-layer greenhouse yield was 14% greater than the double-layer greenhouse yield and can be attributed to the higher daytime VPD and lower RH achieved in the single-layer greenhouse at night. The study established that though the single-layer greenhouse system was cost-effective regarding construction, the operating cost of the single-layer greenhouse was higher than that of the double-layer greenhouse.