Cladding materials in greenhouses or polyhouses are essential components that influence the internal microclimate of the structure. They regulate factors such as light penetration, temperature retention, humidity, and crop protection from pests and harsh weather. Choosing the right cladding material enhances the productivity and efficiency of the greenhouse and should be based on the climatic zone, type of crop, cost, and structural requirements. Cladding materials are generally categorized into two broad groups: flexible and rigid.
1. Polyethylene Film (Flexible Cladding Material)
- Single-layer polyethylene: This is the most widely used cladding material due to its low cost and ease of handling. It allows about 80–85% light transmission and typically lasts for 1–2 years.
- Double-layer polyethylene: Consists of two layers separated by an air gap, improving thermal insulation and reducing heat loss. It has a lifespan of around 3–5 years depending on its quality and UV resistance.
- UV-stabilized polyethylene: Treated with UV inhibitors, making it more resistant to sun damage and extending its usability.
Advantages:
- Lightweight and easy to install and replace.
- Economical and suitable for a wide variety of crops.
- Flexible, making it adaptable to various greenhouse designs.
Disadvantages:
- Shorter lifespan compared to rigid materials.
- Susceptible to physical damage from sharp objects, storms, and strong winds.
2. Polycarbonate Sheets (Rigid Cladding Material)
- Available in single, double, and multi-wall formats.
- Provides excellent light diffusion (80–90%) and thermal insulation due to internal air pockets.
- Offers high resistance to hail, snow, and UV radiation.
Advantages:
- Durability of 10–15 years or more with proper maintenance.
- Superior mechanical strength and insulation properties.
- Helps reduce energy costs for heating or cooling the greenhouse.
Disadvantages:
- Higher initial cost than polyethylene films.
- Requires professional installation and support framework.
3. Glass Panels
- Traditionally used for permanent greenhouses, especially in temperate regions.
- Allows maximum light transmission (up to 95%).
- Can be used in single or double glazing for improved insulation.
Advantages:
- Extremely long-lasting (20–25 years or more).
- Unaffected by UV degradation.
- High clarity for sunlight, ideal for photosynthetic crops.
Disadvantages:
- Fragile and heavy, requiring robust structural framing.
- High capital investment and repair costs.
- Can pose safety risks in case of breakage.
4. Acrylic Sheets
- Rigid transparent plastic, aesthetically similar to glass.
- Allows light transmission around 85–92%.
- More durable than glass and less prone to breakage.
Advantages:
- Strong and impact-resistant.
- UV resistant and long-lasting under regular use.
- Lightweight compared to glass, easier to handle and install.
Disadvantages:
- More expensive than polyethylene films.
- May turn yellow over time with continuous UV exposure.
5. Shade Nets (Supportive/Partial Cladding)
- Typically made from HDPE plastic and used in net houses or as inner cladding during high summer temperatures.
- Available in various shade percentages (e.g., 35%, 50%, 75%).
- Acts as a barrier against excessive heat, pests, and harsh sunlight.
Advantages:
- Provides a cooler microclimate for delicate crops.
- Enhances ventilation and reduces heat stress.
- Reduces incidence of pest and insect attacks.
Disadvantages:
- Not suitable for rainy or windy weather as a primary covering.
- Lower insulation capacity and light retention compared to solid claddings.
Selection Criteria for Cladding Material
- Climatic Conditions: Consider wind speed, temperature extremes, humidity, and solar radiation.
- Crop Requirements: Light sensitivity, temperature range, and humidity needs of the plant.
- Cost Factors: Initial installation cost, replacement cycle, and maintenance expenses.
- Durability: Resistance to UV, weather, pests, and physical stress.
- Energy Efficiency: Ability to insulate and reduce heating/cooling needs.
- Light Transmission: Compatibility with crop’s photosynthetic needs (PAR levels).
Conclusion
Selecting the right cladding material for greenhouses or polyhouses is crucial for maximizing crop yield, reducing operational costs, and ensuring sustainability. While polyethylene is best for budget-friendly and short-term use, polycarbonate and glass are ideal for long-term, high-investment ventures focused on quality and durability. A well-informed decision based on local climate, crop type, and economic feasibility leads to better returns and efficient greenhouse management.
