Architectural glass is widely used in our daily life,such as glass greenhouse/conservatory-Single piece tempered glass,Glass balustrade/canopy-laminated glass,Glass curtain wall-double glazing insulated glass.But glass a good thermal conductive material,Heat conduction through the glass occurs every second causing energy loss.In buildings, 1/3 of the energy is lost through the conduction of glass. Energy efficiency has increasingly valued by architects and developers to minimize the energy consumption of the building.
1 Main parameters of glass energy efficiency evaluation
There are usually three forms of heat transfer: convection, radiation, and conduction. The parameters that measure energy propagation through glass are thermal conductivity and U value , solar transmittance, shading coefficient, SHGC(heat transfer in a stable condition).
Details here:Glass terminology
Let’s compare the normal architectural glass energy efficiency first:
| Glass | U value | Tsol% | SC | Application |
| 4mm clear tempered glass | 5.8 | 83 | 0.99 | Greenhouse Glass |
| 6mm Bronze tinted glass | 5.8 | 45 | 0.68 | Glass spandrel |
| 6+1.52+6 tempered laminated glass | 5.4 | 64 | 0.85 | Point fixed facade |
| 6+12A+6 insulated double glazing | 2.8 | 63 | 0.83 | Facade/curtain wall |
| 6 low e+12A+6 insulated double glazing | 1.6 | 30 | 0.45 | Facade/Curtain wall |
Lower U value and SC means better glass energy efficiency.
2 Energy efficient glass classification
The main energy efficient glass are tinted glass, coated glass, insulated glass, vacuum glass.
2.1 heat absorption glass-tinted glass
The energy efficiency of the heat absorbing glass is converting the light energy into heat energy when the sunlight passes through the glass.
The main color of heat absorption glass are:Green,blud,grey ,bronze and even pink glass.
2.2 coated glass
There are two types coated glass:reflective glass (also called solar control glass) and low emissivity glass.
The reflective glass is coated film on the glass surface to have a certain reflection effect.It can reflect the solar energy back into the atmosphere to block the entry of solar energy into the room.But the visible light transmittance of the glass decreases as the reflectance increases.
Ordinary flat glass has a high emissivity, usually 0.84. Low e coated glass surface radiance lower than that of ordinary glass to reduce heat loss. From single silver low e ,to double silver low e ,and then now triple silver low e coating,the more silver layers inside the coating,the lower emission will decrease U valie and Solar coefficient.
2.3 insulated glass
Insulated glass,or double glazing has a good thermal insulation because the air space between glass limit the convection and conduction heat transfer of the glass.insulating glass collect the advantages of itself and low e coated glass and playing a better role in energy conservation.
| Glass | U value | Tsol% | SC |
| 6+12A+6 | 2.8 | 63 | 0.83 |
| 6 Reflective 60+12A+6 | 2.7 | 37 | 0.52 |
| 6 Single low e 60+12A+6 | 1.8 | 33 | 0.53 |
| 6 Double low e 60+12A+6 | 1.6 | 30 | 0.38 |
| 6 Triple low e 60+12A+6 | 1.6 | 21 | 0.26 |
More low E coated glass performance data,click here:Morn-coated glass performance data
2.4 vacuum glass
Vacuum glass is currently the best energy efficient glass. Vacuum glass creates a vacuum between two sealed glass sheets to make the conduction heat between glass and glass close to zero.While for technology and costs reason,vacuum glass hasn’t been applied in large scale,in the next 20-30 years,vacuum glass will replace insulated glass once price going down.
With the continuous development of glass processing technology, more energy efficient glass appears, to minimizes energy loss, the right glass must be selected based on budget and climate,and even glass location. Only when glass is selected according to local conditions can energy-saving glass fully utilize energy efficient features.
Morn Building Materials is professional architectural glass supplier from China,with Morn’s technical support and quality assured low e coatings,we’re confident to create convenient living space with minimum thermal losses.
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