In simple terms, offline coating has better performance but requires encapsulation protection. The online coating performance is slightly inferior but more durable and sturdy.
Detailed explanation and metaphor
1. Online CVD Process
A vivid metaphor for craftsmanship: just like "glazing and firing ceramics". When the glass water is still in a red-hot and soft state, the coating material is directly "sprayed" onto it. The coating layer and the glass are fused together at high temperatures, forming an integrated whole.
Advantages
Durable and sturdy: The greatest advantage. It can be used alone and does not need to be made into insulating glass for protection.
Flexible processing: It can easily undergo deep processing such as tempering and bending tempering without changing its performance.
Good stability: Resistant to acids and alkalis, anti-oxidation, and has the same service life as the glass itself.
Disadvantage
The performance ceiling is relatively LOW: Due to process limitations, it is impossible to coat a pure silver layer, a high-performance and low-emissivity material. Therefore, its heat insulation and heat preservation performance (especially the U value) has a theoretical upper limit and is not as good as the top-grade offline LOW-E.
2. Off-line Sputtering Process
A vivid metaphor for craftsmanship: It's like "inkjet printing on photo paper". On the already cooled and cut large glass plate, it is sent into a huge vacuum machine, where ions "bombshell" the metal target material, causing metal atoms to sputtered out and "print" layer by layer on the glass surface.
Advantages
Outstanding performance: The greatest advantage. It can precisely deposit complex film systems with up to 10 or more layers, especially including one or more layers of pure silver (Ag), which is the key to achieving extremely low U values and selectivity. The performance of Double Silver and triple silver LOW-E is beyond the reach of online processes.
Attractive appearance: More diverse colors, wider range of light transmittance, and better visual effect.
Disadvantage
The film layer is delicate: Just like a "soft film", it will oxidize and fail when exposed to air, and even minor scratches can cause damage. Therefore, it must never be used as a single piece. Insulating glass or laminated glass should be synthesized as soon as possible after coating, and the film layer should be protected in a sealed inert gas environment.
How to choose?
The situation of choosing online LOW-E:
LOW-E glass needs to be used in single pieces (such as single-piece curtain walls, skylights, interior partitions, and refrigerator doors).
The project budget is limited and the requirement for ultimate insulation performance is not high.
The environment is highly corrosive, and higher durability of the film layer is required.
The situation where offline LOW-E is selected:
The vast majority of insulating glass used in building doors, Windows and curtain walls.
Pursue the highest energy-saving standards (such as passive houses and zero-energy buildings).
I hope to enjoy a wider field of light and a more natural appearance color.
In conclusion, online coating exces in "sturdiness" and "convenience", while offline coating is superior in "high performance" and "aesthetics". In modern architecture, to meet the highest energy-saving requirements, high-performance offline LOW-E insulating glass is the absolute mainstream choice.
