Materials of Construction for Traditional Greenhouses

Traditional and low-cost greenhouses are typically designed to be simple, affordable, and functional. They often utilize locally available and inexpensive materials while maintaining effective microclimate control for plant growth. Here’s a detailed discussion of the materials used:

Traditional greenhouses are built with robust and durable materials, prioritizing long-term use and stability. Common materials include:

Wood Wood has been used historically for greenhouse frames due to its availability and workability. Hardwood (like teak or cedar) and softwood (like pine) are commonly used.

• Advantages: Wood is a poor conductor of heat, maintaining a stable temperature. Blends well with garden landscapes and has a classic appearance. Workability: Easy to cut, shape, and assemble with basic tools.
• Disadvantages: Susceptibility to Rot and Pests: Requires regular maintenance, painting, or chemical treatment. Limited Lifespan: Prone to warping, cracking, and decay over time, especially in humid climates.
• Applications: Used in traditional glass greenhouses and cold frames. Ideal for smaller greenhouses or hobby greenhouses in residential gardens.

Glass Glass is the oldest and most traditional covering material for greenhouses, known for its excellent light transmission.

• Properties: Light Transmission: High clarity with 90-95% light transmission. UV Stability: Does not degrade under UV exposure, maintaining transparency for decades.
• Advantages: Long Lifespan: Extremely durable and weather-resistant. High Light Quality: Provides full-spectrum sunlight, ideal for plant growth. Aesthetics: Clear visibility and elegant appearance.
• Disadvantages: Fragility: Susceptible to breakage from hail, high winds, and impacts. Weight and Installation: Heavy and requires a strong supporting frame, increasing construction costs. Cost: Expensive compared to plastic films or rigid panels.
• Applications: Used in high-end traditional greenhouses, botanical gardens, and conservatories. Suitable for permanent structures requiring high aesthetics and light quality.

2. Low-Cost Greenhouse Construction Materials Low-cost greenhouses are designed to minimize construction costs while providing a suitable environment for crop growth. Common materials include:

 Bamboo Bamboo is an affordable, locally available, and sustainable material widely used for greenhouse frames in tropical and subtropical regions.

• Properties: Good tensile strength, flexible, and lightweight.  Resistant to insects and decay when properly treated.
• Advantages: Inexpensive and readily available in many rural areas.  Eco-friendly and renewable material.  Simple to cut and join using basic tools and techniques.
• Disadvantages:: Prone to decay and weathering unless treated with preservatives. Not suitable for heavy coverings like glass.
• Applications: Used in low-cost poly-houses, shade nets, and temporary structures. Ideal for small-scale farmers and community gardening projects.

Polyethylene Film (PE Film) Polyethylene film is the most commonly used covering material for low-cost greenhouses. It is flexible, lightweight, and affordable.

• Properties: Ranges from 80 to 200 microns. High (80-90%) but decreases over time due to dust and UV degradation. Enhanced with UV stabilizers to extend lifespan (up to 3-4 years).
• Advantages: Much cheaper than glass or polycarbonate. Lightweight and easy to install over bamboo or metal frames.Can be used for various greenhouse designs, including tunnels and low tunnels.
• Disadvantages: Susceptible to tearing, UV degradation, and weathering.  Water droplets can form on the inner surface, reducing light transmission and promoting fungal diseases.
• Applications: Widely used in low-cost poly-houses, hoop houses, and high tunnels. Suitable for seasonal vegetable and flower production.

Netting (Shade Nets and Insect Nets) Shade nets are used to reduce sunlight intensity and provide a cooler environment, while insect nets protect crops from pests.

• Properties: Available in different shading percentages (30%, 50%, 75%) depending on crop requirements. Made from UV-stabilized polyethylene or polypropylene.
• Advantages: Inexpensive and easy to install. Regulates temperature and light, reducing heat stress. Insect nets prevent pest entry, reducing pesticide usage.
• Disadvantages: Prone to tearing and degradation under harsh weather conditions. Excessive shading can affect photosynthesis and crop yield.
• Applications: Used in shade houses, nurseries, and low-cost greenhouses for vegetables and ornamental plants. Ideal for tropical and subtropical regions to protect crops from intense sunlight and pests.

Other Low-Cost Materials  Used for shading in low-cost greenhouses, especially in rural areas.  Economical framing option for temporary structures.  Recycled plastic sheets are sometimes used to minimize costs further.

Summary and Comparison

Modern Materials for Greenhouse Construction

In modern greenhouse construction, the choice of material plays a crucial role in determining the structure’s durability, light transmission, thermal efficiency, and overall cost. Here’s an in-depth discussion of the commonly used modern materials:

Polyvinyl Chloride Film (PVC Films) PVC films are flexible and transparent plastic sheets used as greenhouse covers. They are lightweight, easy to install, and can be fixed over metal or wooden frames.

• Properties: Thickness: Typically 100 to 200 microns. Transparency: High light transmission (80-85%). Durability: Moderate lifespan of 2-3 years with UV stabilizers.
• Advantages: Cost-Effective: PVC films are cheaper than glass or polycarbonate panels. Flexibility: Easy to shape and install over various greenhouse structures. Light Diffusion: Provides uniform light diffusion, which enhances plant growth.
• Disadvantages: UV Degradation: Tends to become brittle and discolored under prolonged UV exposure. UV stabilizers are required to enhance lifespan. Thermal Expansion: Expansion and contraction due to temperature changes can cause wrinkles or tears.
• Applications: Widely used in low-cost poly-houses, nurseries, and temporary greenhouses. Suitable for seasonal crop production due to its short lifespan.

Tefzel T2 Film Tefzel T2 is a high-performance fluoropolymer film known for its exceptional light transmission and durability. It is a copolymer of ethylene and tetrafluoroethylene.

• Properties: Transparency: Up to 95% light transmission, ensuring maximum sunlight penetration. UV Resistance: Superior resistance to UV degradation, maintaining clarity for over 10 years. Durability: High tensile strength and resistance to extreme weather conditions.
• Advantages: Energy Efficient: Retains heat effectively, reducing heating costs in colder climates. High Impact Resistance: Withstands hail and wind loads. Self-Cleaning Surface: Due to its non-stick properties, dust and debris slide off easily, maintaining high light transmission.
• Disadvantages: High Cost: More expensive than traditional PVC or polyethylene films. Special Installation Requirements: Requires specific adhesives and fastening methods.
• Applications: Used in high-tech commercial greenhouses and research facilities where maximum light transmission is essential. Ideal for long-term installations due to its durability and low maintenance.

Polyvinyl Chloride Rigid Panel These are rigid, transparent panels made of PVC, offering more structural stability than flexible films. They are manufactured in corrugated or flat sheets.

• Properties: Thickness: Typically 0.8 mm to 3 mm. UV Resistance: Coated with UV stabilizers to prevent yellowing and brittleness. Fire Retardant: Self-extinguishing property in case of fire.
• Advantages: Durability: Lasts longer than flexible PVC films due to its rigidity and strength. Maintenance Free: Smooth surface resists dust and dirt accumulation. Impact Resistance: Withstands moderate impacts without breaking.
• Disadvantages: Thermal Expansion: Can expand and contract with temperature changes, affecting the fitting. Limited Light Transmission: Slightly lower light transmission compared to glass.
• Applications: Used in semi-permanent and permanent greenhouse structures. Suitable for sidewalls and roofs in small to medium-sized greenhouses.

Fiberglass-Reinforced Plastic (FRP) Rigid Panel FRP panels are composed of polyester resin reinforced with fiberglass, making them strong and lightweight. They are available in corrugated or flat sheets.

• Properties: Transparency: Moderate light transmission (70-85%). Strength: High tensile strength and impact resistance due to fiberglass reinforcement. Insulation: Provides good thermal insulation for maintaining optimal greenhouse temperatures.
• Advantages: Durability: Highly resistant to corrosion, chemicals, and weathering. Impact Resistance: Withstands hail, wind, and other environmental impacts. Light Diffusion: Scatters light effectively, reducing shadow effects and promoting uniform plant growth.
• Disadvantages: Discoloration: Tends to yellow over time due to UV exposure. High Cost: More expensive than PVC but cheaper than glass or polycarbonate.
• Applications: Commonly used in commercial greenhouses for walls and roofs. Ideal for high-wind and coastal areas due to its corrosion resistance.

Acrylic and Polycarbonate Rigid Panel

Acrylic Panels:  Acrylic is a transparent thermoplastic with high clarity and weather resistance.

• Properties: Light Transmission: Excellent light transmission (up to 92%). UV Resistance: Naturally UV resistant, maintaining transparency for longer periods.
• Advantages: Optical Clarity: High transparency and gloss, ideal for display greenhouses. Lightweight: Easier to handle and install compared to glass.
• Disadvantages: Brittleness: More prone to cracking under high impact than polycarbonate. Cost: More expensive than PVC but cheaper than polycarbonate.
• Applications: Used in ornamental greenhouses, garden centers, and exhibition greenhouses.

Polycarbonate Panels:  Polycarbonate is a high-performance plastic known for its strength, durability, and thermal insulation. Available in single, double, or multi-wall configurations.

• Properties: Impact Resistance: 250 times stronger than glass, making it virtually unbreakable. Light Diffusion: Even light distribution, promoting uniform plant growth. Insulation: Multi-wall polycarbonate provides excellent thermal insulation.
• Advantages: Durability: Highly resistant to impact, UV radiation, and extreme weather conditions. Energy Efficiency: Retains heat effectively, reducing heating costs. Lightweight and Flexible: Easy to cut, handle, and install.
• Disadvantages: Cost: More expensive than PVC, acrylic, and FRP panels. UV Protection Required: Requires UV coating to prevent yellowing and degradation.
• Applications: Widely used in modern commercial greenhouses, botanical gardens, and research facilities. Ideal for regions with harsh weather conditions due to its durability and insulation properties.

Summary and Comparison