Greenhouse and Tunnel Cover Materials
topic
Greenhouse cover materials regulate light transmission, thermal retention, humidity, and condensation drip for protected cultivation. LDPE film (100–200 µm, single or double layer) is the dominant material (70% market share) with light transmission of 87–92% PAR, UV blocking (UV absorber EVA 0.5–1.5%), and anti-drip treatment (SiO₂ or anti-drip additives preventing condensation droplets that reduce transmission by 10–15% and cause Botrytis disease). Service life of 1–4 years. Thermic IR-absorbing films (EVA + IR absorbers, ethylene vinyl acetate copolymer with 18–28% VA content) reduce nocturnal heat loss by 30–40%, maintaining minimum night temperature 3–5°C above untreated PE. Polycarbonate panels (4–16 mm twin-wall or triple-wall, light transmission 70–82%, U-value 1.5–3.0 W/m²·K) offer 10–15 year service life at 3–5× cost of PE film. Woven HDPE (200–350 g/m², 40–50% shade, white) for low tunnel crop covers provides frost protection to −3°C and wind reduction of 40–60%. Global greenhouse cover market exceeds $3.4 billion; Netherlands, Spain, and China account for 65% of global greenhouse area of 500,000 ha.
Role
Greenhouse cover materials determine the thermal environment, light quality, and disease pressure within protected cultivation systems, with cover selection being the single most important capital decision determining crop growth rate, energy cost, and achievable yield for high-value vegetable and floriculture producers.