Only when the low e film coating contact with air, the low e glass could effectively reduce the thermal exchange between the glass surface and air, then the heat transfer coefficient (U value) could be lowered and have better energy saving performance. If the low e glass film is in the inner surface of the laminated glass, then the glass surface which contact with air isn’t low e film coating, the thermal exchange is same as normal float glass, which couldn’t reduce the U value of low e laminated glass, and lose the advantage of limitation of heat transfer because of temperature difference, the heat retention for the low e film also disappeared. But the characteristic that reflect the infrared ray will be kept, though couldn’t match the performance of insulated glass, but still have the shaded effects.
The test data could show this clearly. To compare, we use the normal laminated glass, low e laminated glass with same structure (low e film surface in the inner), low e insulated glass, and take the 300W IR Lamp to irradiate the three kinds glass surface from 30mm distance, then to measure the other surface temperature after 30 minutes later, the results is as followed,
According the results, the temperature for the low e laminated glass and float laminated glass is similar, this conform to the situation that the K value is same between this two laminated glass. The 1℃ temperature difference should be caused by the absorbed heat on the back glass pieces is lowered by low e film coating, this also conform to the situation that the difference on the shading coefficient, the same low e film coating in the insulated glass could have good energy saving performance.
Please note that though the low e film coating in the inner of the laminated glass, the energy saving performance will be affected much. But if the low e film coating is in the outside surface of the laminated glass, the energy saving performance will be also improved much.
Post time: Sep-01-2022