5 Points in design glass facade with Vacuum glass
When design a glass facade with vacuum glass,architects and designers are always confused on some key points,such as vacuum glass equivalent thickness,vacuum glass lifetime,vacuum glass wind resistance,this posts collect some conclusion of vacuum glass articles and work as ref when you design a vacuum glass facade.
Vacuum glass equivalent thickness
Under the external load of vacuum glass, the two pieces of glass always maintain the same deformation and generate the same bending stress. Therefore, to study the strength and stiffness of vacuum glass, vacuum glass can be regarded as a whole and analyzed as a single piece of glass. However, the load-bearing deformation performance of vacuum glass is not as good as that of a single piece of glass equal to its total thickness.
(1) The length and width of vacuum glass have no obvious effect on the equivalent thickness.
(2) The thickness of the vacuum glass substrate has an influence on the equivalent thickness, and the greater the thickness of the substrate, the smaller the equivalent thickness coefficient (eg /t total) is.
(3) The equivalent thickness is basically the same whether it is calculated by equal deflection or equal stress.
(4) Through the above analysis, the following important results can be obtained:
The equivalent thickness coefficient of N3+V+N3 vacuum glass can be taken as 0.95,
The equivalent thickness coefficient of N4+V+N4 vacuum glass can be taken as 0.90,
The equivalent thickness coefficient of N5+V+N5 vacuum glass can be taken as 0.85
(5)Since the elastic modulus of semi-toughened, tempered and float glass is basically the same, whether the vacuum glass adopts ordinary glass substrate or tempered or heat strengthened glass as the substrate, it has little effect on the equivalent thickness.
Vacuum glass wind resistance
Below table shows the actual test based on glass solder vacuum glass:
|Glass Type||Glass Combination||Size-mm||Wind Resistance -Pa|
|HS VIG||T5 + V+T5||1500*850||±5000|
|HS VIG||T5 + V+T5||2600*1600||±4103|
|HS VIG+ DGU||T5 + V+T5 +9A+6||2600*600||±5000|
|HS VIG+ LAMI||T5 + V+T5 +1.52PVB+6||2600*1600||±5000|
Landvac VIG wind resistance also reached ±7200Pa based on 5 +0.3V+4.
- The wind pressure resistance of composite vacuum glass is better than that of normal vacuum glass.
- The smaller the size, the higher the wind resistance of vacuum glass.
For curtain wall projects, especially for super-large or ultra-high-rise curtain walls, and composite vacuum glass should be selected. Namely vacuum + insulating glass or vacuum + laminated glass. For buildings with higher safety factor requirements, any combination of laminate+ vacuum + laminate VIG +IGU can be used.
How is the vacuum sealed windows U value
Since the area ratio of profiles accounts only 30% of whole window ,balance 70% are glass. due to the reduction of the same heat transfer coefficient value, the influence of profiles on building exterior windows is relatively smaller than that of glass.
When the frame-to-window ratio is about 30%, the PVC casement window U value can basically only reach 2.1 W/m2·K,and thermal break aluminum alloy windows can only reach 2.5 W.Both them reached a bottleneck stage, and the emergence of low-emission coating (Low-E) vacuum glass solves this problem.
Below table shows the windows U value difference based on different windows and glass.
|6C+9A+6C||6 LE+9A+6C||6 LE+0.3V+6C|
|Glass U value||2.7||1.8||0.6|
|Window U value-|
60 PVC window
|Window U value-|
60 aluminium window
With HaanGlas lower U value VIG ,the window U value can be decreased even lower.
Sealed edge reliability after installation
After installation,vacuum glass edge are affected by the glass weight,temperature difference (indoor and outdoor),and wind load.Test result of solder edge sealing VIG performance include:
Three point flexural strength: 33.16Mpa
Sealed edge tensile strength: 0.604 Mpa
Sealed edge shearing strength: 3.45Mpa.
- Based on glass combination : 6+1.52PVB+6+0.3V+6+9A+6, size 2800*1800mm, sealed edge width 10mm.
Edge shearing strength 0.0161 ,design strength 0.575Mpa,which is far less than 3.45Mpa
- Temperature .Even under 80℃ temperature difference, the shearing strength is below 0.06Mpa,still far lower than 3.45Mpa.
- Wind load.Assuming that the edge of the vacuum glass is in a free state and is not constrained by the frame, the edge of the vacuum glass will bend under the wind pressure, and the maximum stress is generated at the maximum bending moment, that is, the center of the edge.Calculated bending strength is 2.99Mpa,far lower than 33.16Mpa.
The edge stability and strength can be ensured absolutely.
Vacuum glass Lifetime and vacuum degree
Vacuum glass is subjected to long-term temperature difference changes and sun exposure during use, and part of the gas on the inner surface and deep layers of the glass will be released, which may lead to a decrease in vacuum. Therefore, placing a getter in the vacuum glass can improve and maintain the vacuum degree of the vacuum glass, thereby prolonging the VIG lifetime.
Evaporative getter refers to the getter in which the getter material plays role only when the getter material evaporates and after deposition and film formation.
It can effectively absorb N, H, O, CO, CO, H, O and other gases in the range from room temperature to 20 ℃, and it is the best for oxidizing gases such as CO. For H, O molecules, the reaction speed of the barium film is extremely fast, and it is easier to obtain a large area of the inhalation film during evapotranspiration.
Calculation shows that for a 5+V+5 vacuum glass 5+V+5,size 1800mm × 2800mm, the total gas output in 50 years is 0.13Pa·L. At present, the inhalation volume of the getter placed in the vacuum glass is about 1.14Pa·L.so the vacuum life of the vacuum glass can be guaranteed for 50 years.
HaanGlas is your turnkey vacuum glass supplier in China,kindly contact us if you encounter problems when designing your glass facade with vacuum glass.