How Long is The Lifespan of Door and Window Glass?

Ordinary Glass

There is no "aging" problem in the natural environment.

The chemical composition of glass is very stable, and in its natural state, glass will not be affected by sunlight, rain, or fog, resulting in performance degradation; Ordinary acidity and alkalinity do not cause harm to glass, as we can see from the chemical experiment vessels we used when we were studying.

There are usually only two situations that affect the lifespan of glass: humid air and high temperature. Continuous humid air can cause glass to mold, but at room temperature, the rate of mold growth on glass is very slow, usually taking several months. In normal usage environments, there is rarely continuous humid air for several months, so glass exposed to air will not mold. Generally, mold growth of glass occurs during overlapping storage, and glass is more prone to mold growth when stored in damp warehouses or exposed to rain. Generally speaking, raw glass without tempering is more prone to mold than tempered glass.

Without considering the factor of thermal explosion, temperatures below 300 ℃ have no effect on the lifespan and chemical stability of glass. But above 300 ℃, the physical and chemical properties of glass will change with the increase of temperature. Physically speaking, typical glass begins to soften around 600 degrees. In terms of chemical properties, an increase in temperature will cause crystallization inside the glass, gradually transforming it from transparent to blurry. The process of glass crystallization losing transparency at 700 ℃ takes several days, while at 300 ℃ it may take several months or even years. At room temperature, the crystallization and blurring of glass may take tens of thousands of years, so it can be ignored.

The Lifespan of Tempered Glass

Physical tempering is the process of heating and then rapidly cooling glass, which changes the structure between molecules inside the glass; Chemical tempering is used for ion exchange of the molecular structure on the surface of glass at high temperatures; Both methods permanently alter the microstructure of glass materials. Therefore, unless there is high temperature and strong chemical reaction, the characteristics of tempered steel will not decay or change over time under normal use.

The Lifespan of Insulating Glass

Hollow glass is a combination product composed of glass substrate, spacer frame (aluminum strip), desiccant (molecular sieve), and sealing material (butyl rubber, polysulfide rubber or structural adhesive). In the composition of insulating glass, glass and aluminum frame are usually very stable, and the lifespan of insulating glass depends on the lifespan of molecular sieves and sealing materials.

In the composition of the insulated glass system, the glass is very stable, and as we mentioned earlier, the glass substrate does not need to consider aging under normal use; The recommended aluminum bars for standard hollow are all surface anodized. The physical and chemical properties of aluminum strips treated with surface anodization are very stable under conventional conditions. Even for aluminum bars that are almost without surface anodizing treatment, oxidation may occur during use, causing the aluminum bars to lose their luster, but this does not have a significant impact on the performance of the aluminum bars themselves.

For insulated glass, we should recognize that the value of constructing an insulated system lies in having a sealed and dry cavity in order for the insulated glass to provide insulation and sound insulation. Due to changes in environmental temperature, the gas inside the hollow cavity is always in an expanding or compressing state, causing the hollow glass sealing system to always be under stress. At the same time, ultraviolet radiation, water, and moisture in the environment will accelerate the aging of the sealing system, leading to the accelerated entry of water vapor into the hollow cavity. When a large amount of water vapor appears in the cavity of the insulating glass, the insulating glass has already failed, and the failure of the insulating glass means that the service life of the insulating glass is terminated. The key to ensuring that the insulated glass does not fail is the desiccant and sealing material.

Regarding the lifespan of insulating glass, Chinese glass companies initially referred to American standards and introduced the concept of a 10-year warranty period; In the national standard GB/T11944-2012 for insulating glass, a reference agreement on the service life of insulating glass is proposed for the first time, proposing the concept that "the expected service life of insulating glass should be greater than 15 years". In fact, the lifespan of insulating glass is closely related to the selection and processing technology of insulating glass materials, and is also influenced by many factors such as the composition of the insulating glass layout and the usage environment, making it difficult to simply quantify. For insulated glass that has already been installed on the wall, a relatively simple measurement method is actually to measure the dew point or the air humidity in the interlayer.

The Lifespan of LOW-E Glass

The lifespan of LOW-E glass mainly depends on the lifespan of the hollow sealing system in which it is located. We know that the main constituent materials of LOW-E film layer are metals, alloys, metal oxides, and metal nitrides. Metal nitrides are generally used as protective layers in film structures, and their properties are very stable. Metal oxides and alloy layers are generally used as dielectric layers in the film layer to connect the silver layer and the protective layer, and their properties are also relatively stable. The silver layer in LOW-E is relatively active, but its oxidation is conditional and requires the presence of water vapor.

Therefore, as long as the insulating glass does not fail, there is basically no need to separately consider the lifespan of the LOW-E film layer.

The Lifespan of Laminated Glass

Laminated glass is a composite glass product in which two layers of organic polymer intermediate films are sandwiched between the glass, and after processing, the glass and intermediate films are permanently bonded together. Laminated glass ensures personal safety by preventing fragments from sticking to the film even if the glass breaks, effectively preventing incidents such as stabbing and falling through.

The lifespan of laminated glass mainly depends on the material of the interlayer. Normally, wet laminated glass and EVA laminated glass are mainly used for indoor partitions and are not suitable for building doors, windows, or curtain walls. Wet laminated glass and EVA laminated glass will accelerate aging under sunlight, and yellowing will occur after 1-2 years. From 2-3 years, delamination bubbles, ice bubbles, and fogging will gradually appear. Generally speaking, the aging rate of wet laminated glass is much faster than that of EVA laminated glass. EVA laminated glass can have a lifespan of over 10 years when used indoors to avoid direct sunlight.

PVB and SGP laminated glass, commonly used as doors, windows, or curtain walls, have much better aging resistance. The most typical failure of laminated glass PVB and SGP is debonding, which means that the glass and spacer layer detach, losing the safety characteristics of laminated glass. There are currently no relevant standards or specifications in China regarding the lifespan of PVB and SGP laminated glass. At present, domestic glass processing enterprises generally refer to foreign PVB and SGP suppliers' relevant materials to provide a product warranty period of 5-7 years.

In fact, the lifespan of PVB and SGP laminated glass is greatly influenced not only by the material of the intermediate layer, but also by the thickness of the intermediate layer, the quality of the laminated glass substrate, and the control of the laminated glass process.