There is a fast, simple and inexpensive way to check if a glass plate is low emissivity. It is necessary to understand not only if the low emissivity film has been applied, but also if it is located on the correct side.
To do this, simply bring a flame, for example a lighter, to the plate and see what color the reflected flames appear.
For example, if the window is double-glazed, we will see three flames reflected.
When these are the same color - usually yellow - it means that there is no low-emissivity treatment.
If, on the other hand, one or two of the reflected flames are darker in color - yellow tending to purplish - then it means that the low-emission film has been applied, generally on the surfaces, facing outwards, of the internal glass.
But how does the film work?
Its chemical characteristics allow it to stop most of the electromagnetic waves due to solar radiation (those of the electromagnetic spectrum with high lambda) to reflect them towards the internal environment and not to let them escape.
As an example, a window with double glazing without treatment disperses about three times more.
Another way, to verify the presence or not of the treatment in question, just as fast, but more sophisticated and more expensive, is to use a laser light thickness gauge for glass.
Source: https://www.architetturaecosostenibile.it/ (Giovanna Barbaro architect and technologist).
