Why is 3.2mm glass usually not recommended?
3.2mm glass falls into the category of thin glass (typically, the thickness of glass specifically designed for greenhouses is 4mm, 5mm or more), and it has some obvious disadvantages in greenhouse environments:
Low strength and poor impact resistance
It cannot effectively resist the impact of hail, crushed stones lifted by strong winds, etc., and has a high risk of cracking.
During installation and daily maintenance, workers' trampling or accidental impact with tools may both lead to cracking.
The structural force-bearing capacity is weak, and the requirements for the flatness and load-bearing capacity of the greenhouse frame are extremely high.
Security issues (key shortcoming) :
3.2mm glass is usually ordinary float glass. When it breaks, it will form large and sharp fragments. Falling from a height can cause serious harm to people and crops. This is the greatest safety hazard in greenhouse applications.
The heat preservation performance is average
Glass itself has a high thermal conductivity and is a good conductor of heat. The K value (heat transfer coefficient) of single-layer 3.2mm glass is very high. It dissipates heat quickly at night in winter and absorbs heat rapidly during the day in summer, resulting in poor energy consumption control.
Strict requirements for the supporting structure:
Due to its thinness and low strength, it requires denser and flatter purlins and grilles for support. Even a slight deformation may cause the glass to break due to stress concentration. This might offset the cost advantage brought by the thinness of the glass.
Under what conditions can it be considered for use?
If the budget is extremely limited and all of the following conditions are met, it may be used in short-term or low-security situations:
Mild climate conditions: Areas with no historical records of hail and strong winds (low wind force level).
Greenhouse type
Small-scale leisure and sightseeing greenhouses: They are not very tall and the flow of people is controllable.
Simple production greenhouse: It has low requirements for lifespan and safety and can be used as a temporary or low-cost solution.
Key measures
Explosion-proof film must be applied: this is the most important remedial measure. Applying high-quality safety explosion-proof film to the inner wall of the glass can stick the glass together when it breaks, preventing fragments from flying and greatly enhancing safety.
Optimize structural design: Adopt smaller division sizes (for example, reduce the 1m x 1m division to 0.5m x 0.5m), and increase support points.
Choose tempered treatment: If 3.2mm glass is used, be sure to choose tempered glass. The impact strength and temperature variation resistance after tempering will be significantly enhanced, and when broken, it will form granular fragments, which is safer than ordinary glass. However, tempered glass has a self-explosion rate and cannot be cut again.
Iii. What are the mainstream recommended solutions in the industry?
For modern professional greenhouses, especially large multi-span greenhouses, the industry standards are usually:
4mm or 5mm tempered glass: This is currently the most mainstream configuration. A good balance is achieved among strength, safety, durability and cost. 5mm is more common and reliable.
4mm tempered ultra-white embossed glass
Ultra-white: It has an extremely high light transmittance (over 91%), which is 3-4% higher than that of ordinary glass. It can significantly enhance the light inside the greenhouse and promote crop growth.
Embossing (scattering) : It converts direct light into scattered light, making the illumination more uniform, preventing plant scorching, and reducing shadows.
Tempering: Ensuring safety.
This is currently the gold standard for high-end planting greenhouses (especially for flowers, seedlings, and high-value-added crops).
Insulating glass: It is used in greenhouses that require higher insulation performance (such as research greenhouses and high-end leisure greenhouses), but the cost and weight increase significantly.
Polycarbonate sheet (PC sheet) : As an alternative solution, it has the advantages of light weight, impact resistance (200 times that of glass), good insulation, and high safety. It is an economical and practical choice for many production greenhouses.
Conclusions and Suggestions
When building new professional production or commercial greenhouses, the use of 3.2mm ordinary float glass should be avoided as much as possible.
If it is necessary to use: Please ensure that at least the conditions of "tempering treatment + explosion-proof film application + mild climate + small compartment design" are met, and be mentally prepared for higher maintenance and replacement costs.
Recommended solution: Allocate the budget to 4mm or 5mm tempered ultra-white embossed glass or high-quality PC boards. From the perspective of safety throughout the entire life cycle, production efficiency and maintenance costs, this is a more economical and reliable investment.
Ultimately, the selection of greenhouse materials requires a comprehensive consideration of climatic conditions, the crops to be grown, the type of greenhouse, the budget, and long-term operating costs. It is recommended to consult a professional greenhouse engineering company for detailed design and scheme comparison.
