Properties of an Ideal Greenhouse Covering Material

The effectiveness of a greenhouse depends largely on the quality of its covering material (cladding). An ideal covering material should provide the right microclimate, durability, and cost-effectiveness for sustainable crop production.

a. Light Transmission

• Should allow maximum solar radiation (85–90%) to pass through for photosynthesis.
• Should transmit photo synthetically active radiation (PAR: 400–700 nm) without significant loss.
• Uniform light diffusion is desirable to prevent shading and ensure even crop growth.

b. Thermal Properties

• Should provide good insulation to reduce heat loss during cold nights.
• Must help in maintaining stable internal temperature.
• Should reduce infrared (IR) radiation loss to conserve energy.

c. Mechanical Strength

• Must withstand wind load, rain, hail, and snow pressure without damage.
• Should be resistant to mechanical wear and tear.
• Lightweight materials are preferred for ease of installation, but they must be structurally strong.

d. Durability

• Long lifespan (ideally 8–25 years, depending on type).
• Should resist UV degradation caused by prolonged sunlight exposure.
• Must not become brittle, discolored, or cracked over time.

e. Weather Resistance

• Must tolerate temperature fluctuations (both hot summers and cold winters).
• Resistant to moisture, humidity, and condensation.
• Anti-drip properties are desirable to prevent water droplets from falling on plants.

f. Fire Resistance

• Should have low flammability and meet safety standards.
• Materials like polycarbonate sheets and glass are better than ordinary polythene in fire safety.

g. Ease of Installation and Maintenance

• Should be lightweight and flexible for easy fixing and replacement.
• Should allow cleaning without damage to the surface.
• Compatibility with available greenhouse structures is important.

h. Cost-effectiveness

• Should balance between initial cost, lifespan, and performance.
• Locally available materials with moderate cost are more suitable for farmers in developing regions.

i. Additional Desirable Properties

• UV Stabilization: Prevents material degradation and reduces harmful UV radiation.
• Anti-dust and Anti-algae properties: Helps maintain transparency.
• Recyclability: Environment-friendly options are preferable.