Assessing greenhouse covering systems for energy efficiency and solar irradiance modulation: A technical review

The selection of sustainable and effective covering systems is essential in greenhouses to ensure optimal insulation, microclimate control, energy management, and proper solar irradiance filtration for plant growth. This study evaluated representative types of greenhouse coverings: uncoated clear glass, Low-Emissivity (Low-E) coated glass, Ultraviolet (UV)-blocking coated glass, polyethylene (PE), polycarbonate (PC), anti-condensation polyethylene (PEAC), and infrared reflective plus anti-condensation polyethylene (IRAC). In our examination and comparisons, we focused on assessing their thermal and optical properties and associated energy performance through simulations across various climate zones using WINDOW, OPTICS, and EnergyPlus. In particular, this study used a full-glazing greenhouse and concluded an estimating model with interior lighting, heating and cooling energy consumption, and total energy. Low-E coated covering systems had the best U-factor among all materials and achieved an average of 15.9% reduction in total energy consumption without much suffering on interior lighting. Meanwhile, both Low-E and UV-coated glass offered desirable lighting quality in the red wavelength range, enhancing metrics such as the red-to-blue (R:B) and red-to-far-red (R:RF) ratios. Additionally, the performance of Low-E deteriorated when condensation formed, highlighting the importance of selecting materials with anti-condensation properties in certain areas where nighttime temperature significantly drops. Additionally, the findings indicated that UV coatings were not optimal for cloudy areas due to their insufficient daylight transmittance. It necessitates increased use of interior lighting to compensate for the lack of natural light. Overall, this research underscores the critical balance between energy and light performance necessary for optimal plant growth. This work aimed to guide the choice of covering systems for greenhouses.