Low-E is shorthand for Low Emissivity.
Emissivity:- the relative power of a surface to emit heat by radiation
- the ratio of the radiant energy emitted by a surface to that emitted by a blackbody at the same temperature.
Since a Low-E surface will emit less heat by radiation, it will also reflect more heat. Window Film manufacturers have utilised this property so that they can make Window Film with insulation. The significance may be missed unless you consider that normal Solar Control film works on the Near Infra-red heat energy but Low-E coating is reflecting Far Infra-red heat energy.
There are many technical challenges to make such a product, not least of which is to protect the Low-E surface coating, since a regular scratch-resistant coating significantly reduces the performance.
- Ecolux 70, E 0.09
- Silver Ag 25, E 0.33
- Silver Ag 50, E E 0.37
- 3M LE35AM, E 0.34
- Single pane clear glass, E 0.84
Related articles:
- Insulation & Low-E
- Particularly the discussion of U-Value