Different types of glass for horticulture use

Greenhouse farming is a widely established practice within controlled environment agriculture, encompassing a variety of infrastructures from simple tunnels to highly automated facilities. These structures cater to cultivating a diverse range of crops, such as vegetables and flowers. Regardless of the greenhouse type in use, numerous opportunities exist to optimize yields and enhance productivity. In this piece, Migo Glass aims to shed light on the influence of glass on greenhouse crop production.

Why choose glass over polycarbonate for greenhouse use?

Glass has consistently been a popular choice and prevalent material in greenhouse construction, despite being more costly than polycarbonate. The myriad of benefits justifies the higher price it offers to greenhouse production.

• Durability: Glass exhibits greater durability and resistance to scratching compared to polycarbonate, which is prone to scratches over time, posing a threat to its light transmission.
• Light transmission: Glass provides superior light transmission and maintains its clarity over time without yellowing or becoming brittle, ensuring consistent, high-quality light for the plants.
• Insulation: Glass provides better insulation, aiding in the maintenance of a stable internal temperature within the greenhouse, which is beneficial for optimal plant growth.
• Aesthetics: Glass lends a traditional and visually appealing aesthetic to greenhouses, making it desirable for specific settings.
• Longevity: Glass offers a longer lifespan compared to polycarbonate, which tends to degrade over time due to UV exposure.

Primary types of greenhouse glass:

1. Annealed glass Annealed glass, the standard type of glass familiar to all, undergoes a heat treatment process followed by controlled cooling to alleviate internal stress gradually. However, this type of glass is relatively weak and prone to cracking or shattering when subjected to rapid changes in temperature on either side. When it breaks, it forms large, jagged shards, posing potential hazards to nearby individuals. It is an affordable option and suitable for wall panels in a greenhouse with minimal exposure to heavy snow and strong winds.

• Pros: Annealed glass is a cost-effective option, stronger than regular float glass, and can withstand some pressure due to its treatment process. Suitable for low-traffic areas and locations with minimal exposure to extreme weather conditions like heavy snow or high winds.
• Cons: It shatters into sharp edges when damaged, rendering it unsuitable for use in high-traffic areas, doors, or greenhouse roofs exposed to harsh weather conditions.

2. Tempered glass Tempered glass, subjected to a specific heat treatment process, induces stress in a controlled manner to increase surface stress relative to internal stress. It is significantly clearer and up to six times stronger than annealed glass, breaking into small, nearly square pieces that pose minimal risk to individuals. This type of glass is suitable for greenhouse roofs, walls, and doors due to its ability to withstand fluctuating temperatures, although it is not recommended for roofs bearing snow loads or strong winds.

• Pros: Tempered glass is much stronger than annealed glass due to additional treatment processes. Capable of withstanding temperatures up to approximately 470 degrees Fahrenheit. When broken, it shatters into small granulated pieces, presenting minimal harm to people. Handles temperature changes better than annealed glass. Available in single- and double-tempered forms with varying tensile strengths.
• Cons: It is more costly than annealed glass but offers greater strength and breakage safety. May crack before complete shattering, possibly affecting the internal heat and humidity of the greenhouse.

3. Diffused glass Also known as frosted or obscured glass, diffused glass is a favored option for commercial greenhouse usage due to its ability to scatter light, reduce shadows, and achieve uniform light distribution for plant growth. Notably, diffused glass minimizes the intensity of direct sunlight, helping to prevent plant sunburn and heat stress, which is particularly advantageous in regions with high solar radiation levels. This type of glass is ideal for enhancing crop yield under the following factors:

• Pros:

1. Improved penetration into the crop.
2. Substantial light gain in all seasons.
3. Reduced shadowing in the greenhouse.
4. Mitigation of crop stress.
5. Effective light diffusion.
6. High light transmittance.
7. Comprehensive haze range.
8. Non-condensation dripping.

• Cons:

1. Cost: Diffused glass may incur higher expenses compared to traditional greenhouse glass, which could pose a significant consideration for growers with budget constraints.

2. Light Transmission: While diffused glass effectively scatters light, it may lead to a slight reduction in overall light transmission compared to clear glass, potentially impacting the growth of light-dependent crops.

3. Limited Application: The advantages of diffused glass may not be equally notable for all types of crops or in all growing conditions, making it less suitable for certain agricultural operations.

All these glass types are available in clear and low-iron versions. The low iron variant offers superior light transmission due to its low parts per million (PPM), resulting in reduced iron content and minimal greenish tint.

AR Coating for Greenhouse Glass

When considering horticulture, increased sunlight entering the greenhouse translates to more light reaching the plants, ultimately resulting in higher achievable yields. Our glass processing line is equipped to apply anti-reflection coatings on either one or both sides of the glass surface (1AR or 2AR), simultaneously reducing sunlight reflectivity to increase the light transmission rate by up to 97%.