The application of architectural curtain wall began at the end of the 19th century, when it was only used for a small part of the building. By the 1950s, with the development of construction technology, glass curtain walls began to be applied to the building envelope on a large scale, By the 1980s, with the development of building curtain wall technology and glass production technology and processing technology, glass curtain walls have been more widely used.
The total amount of China curtain walls in existing buildings exceeds 1 billion square meters, glass facade account over 50%,most of them are used in skyscrapers.Here we introduce the glass panels designs for skyscrapers.
Why glass is the most important curtain wall materials in Skyscrapers?
As a building material, glass has four major characteristics at the same time: transparency, high strength, light weight, and durability.
Glass Light transparency
Glass is a transparent material. The visible light transmittance of clear float glass is 85-89%. Low iron glass reduces the iron element in the glass, making it more crystal clear and translucent, and the visible light transmittance is increased to more than 90%.
The light transmittance of polycarbonate board (PVC board) can reach 75%~80%.
Thin film materials (such as ETFE) can only transmit diffused light, but are opaque.
Glass Strength
Glass is a brittle material, but has high tensile strength. Among the commonly used wall materials, its tensile strength is second only to steel and much higher than other materials.
Glass light weight
The glass bending strength is very high, especially the tempered glass plate. Therefore, the glass panel of the glass curtain wall is very thin,. Even if insulating glass or laminated insulating glass composing of 2 or 3 layers of glass, unit weight is only 40 ~ 80Kg/m2, which is much smaller than the 350 ~ 500kgs/m2 of the concrete wall /㎡.
The glass curtain wall weight is about 1/100 of the building total weight. This creates the necessary conditions for the upward extension of the building height.
Due to its high weight and low strength, stone curtain walls are rarely used in buildings above 400m. Similarly, for skyscrapers above 400m, architects will not choose to use sheet metal due to the requirements of architectural art functions. Above 500m, almost all glass curtain walls. Without glass curtain walls, there would be no super-tall skyscrapers above 500m.
Glass panel designs for skyscraper
- Low iron Glass
Tempered glass has the possibility of spontaneous explosion. Skyscraper glass facade will bring a great risk of spontaneous explosion,and it is extremely difficult to replace the glass after glass breakage. Therefore, effective measures must be taken,including:
- Heat strengthened glass.Surface strength is lower than tempered glass,no breakage possibility.
- Low iron glass with lower iron content. During production, nickel and nickel sulfide content is also decrease.. The spontaneous explosion rate of ultra-white glass after tempering can be reduced to 0.0001, or even lower.
Even though low iron glass is 30% higher than clear glass,considering the decreased future replacing costs,it’s worthwhile to use low iron one to decrease overall costs.
- SGP laminated glass
PVB laminated glass is currently the most widely used glass in curtain wall.While PVB was It was originally developed for automotive glass, not for architectural curtain walls, so it is elastic, relatively soft, and has small shear modulus. PVB laminated glass has small bearing capability and large bending deformation.
Meanwhile the exposed edges of PVB laminated glass are easy to delaminated, after years ,glass will become yellow color.
For skyscraper glass,the interlayer should have below characteristics:
- High bonding strength,high shearing modulus.
- High protection capability against hurricane,earthquake,thefts, and sudden impact to avoid collapse.
- High sustain capability after glass breakage.
- No color change after years.
SentryGlas Plus was invented to fulfill the high structural laminated glass requirement in skyscraper glass facade,large span skylight,oversized laminated glass and all glass structural buildings.
Features of SGP laminated glass:
A.High bearing capability,smaller bending deflection：
The shear modulus of SGP is more than 50 times that of PVB, and the tear strength is 5 times higher than that of PVB.The bearing capacity is twice that of PVB laminated glass of equal thickness,meanwhile under the equal load and thickness, the bending deflection of SGP laminated glass is only 1/4 of that of PVB laminated glass.
B.Excellent edge stability
Edge stability refers to the laminated glass edges durability exposed to atmospheric conditions. PVB glass is not resistant to moisture, it is easy to delaminate under water vapor. The SGP film is not sensitive to moisture, and will not open or separate when used under exposed conditions.So SGP laminated glass is conveniently used for glass railings, canopy, glass fins and other exposed edge components without special edge sealing measures.
- High sustain capability after breakage
Once tempered laminated glass is broken, it will be bent and deformed causing the falling off or collapsing dangers. The risk is greater when the glass is installed horizontally on the skylight.
The SGP interlayer laminated glass has good integrity.The SGP film can bond the broken glass to form a temporary structure after damage. The deformation is small, and it can withstand a certain amount of load and prevent falling.More details:
Post Breakage Strength Testing for Overhead Laminated Glass
- High performance low-E coating insulated glass.
With the development of glass technology,energy-saving is becoming more and more important,especially for skyscrapers with thousands square meters glass curtain wall,the energy used for heating and cooling is awesome.
Clear float glass U value is 5.8w/m2.k,with new double silver low-E coating and triple silver low-E coating,double glazed units U value can be decreased to 1.5-1.6W/M2.K,with more energy saving measurement,such as filling argon into the insulated glass,and warm edge spacer to decrease the thermal conductivity ,glass U value can be decreased to only 1.1-1.2W/M2.K,which contribute to the overall thermal insulation performance of the glass facade.
Function of Low-E coatings:
The low emissivity coating can reflect the far infrared radiation directly,especially the silver layer inside the soft coated low-E coating can reflect 98% far infrared radiation like mirrors.
The coating has little capability absorbing the heat,which will control the glass surface temperature very well, the heat re-radiated out from the glass is little accordingly.
Despite controlling the infrared,the coating as a variety options with different visible light transmittance and SC value(0.2-0.7) to control the ratio of direct solar energy transmitted through the glass,which can be selected by users both in hot and cold areas.
For more details,please check our previous posts:
20 FAQ about low emissivity glass-Glass Guidance
Triple silver low-E insulating glass in LEED buildings
Difference between Single silver low-E,double silver low e and triple silver low e
Conclusions:
- skyscrapers above 500m in height always use glass curtain walls,including stick curtain wall,unitized curtain wall.
- Double laminated insulated glass,or laminated insulated glass are priority for skyscrapers.Glass can be heat strengthened ,or low iron glass to decrease glass spontaneous breakage ratio.
- SGP interlayer is should be considered for the middle layer film. To improve the safety of the glass curtain wall.
- High performance low-E coatings-double silver low-E,triple silver low-E coatings are applied in the insulated glass to increase facade thermal insulation performance.
Case study:
- CITIC-BEIJING
Located in Beijing, China CITIC is the world’s tallest building with 8 degrees of seismic fortification, with 108 floors above ground and a height of 528m (Figure 48). The stick curtain wall, the glass configuration is tempered low iron glass with double silver low-E coating + SGP laminated+insulated glass.
- Tianjin 117 tower
Tianjin Gaoyin 117 has a height of 592m and 117 floors. The 32, 63, 94 and 115~116 floors are high-rise lobbies, with a diamond-shaped glass roof on the top.
The curtain wall has a total area of 147,000 square meters composed with 20,000 unit. The standard unitized curtain wall unit is 4.3m X 1.5m, with 14,000 unit panels;
Glass curtain wall: (8mm+1.52PVB+8mm)+ 12A + 8mm low iron tempered PVB laminated glass.
High-altitude lobby: (8mm+1.52PVB+8mm)+ 12A + 12mm / 10mm low iron tempered PVB laminated glass.
- Guangzhou tower.The height of the Guangzhou Tower is 600m, and the height of the glass curtain wall is 460m .The stick glass curtain wall adopts triangular unit panels with a size of 1500mm X 3500mm. Double laminated semi-tempered insulating glass, (8mm+1.52mmSGP+8mm)+12mmA+(8mm+1.52mmSGP+8mm)
Morn is your turnkey glass manufacturer and supplier in China,we manufacture low iron SGP laminated insulated glass for global projects,welcome contact us for more info.
Contact us:
Qingdao Morn Building Materials Co.,Ltd
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