Do You Have Low-E Windows? Here is a Quick Way to Find Out.

25 Nov.,2022


low-e glass vs clear

When discussing window film options with a property owner, we sometimes are unaware of the make-up of a particular window. The owner may think that they have Low-E windows, but have no paperwork to confirm that fact. In that case, without the use of a Low-E detection meter, is there a way to determine if a window has a Low-E coating and on what surface of the glass it is applied? Fortunately, the answer is yes.

Let’s first define the differing surfaces of a window so that we are all on the same page. A basic double pane window is constructed like the picture below. The surface numbers allow everyone to understand exactly what surface of a dual-pane unit everyone is referring to.

Starting from the outer-most surface, the numbers are as follows:

    • Surface 1: Outside surface of the outside pane of glass.
    • Surface 2: Inside surface of the outside pane of glass.
    • Surface 3: Outside surface of the inner pane of glass.
    • Surface 4: Inside surface of the inner pane of glass.


So, now that we understand the construction of the glass unit, how can we tell whether there is a Low-E coating applied. The answer is really very simple and is illustrated in the graphic below.

You can simply light a match or a lighter and hold it near the glass. Pay attention to the 4 flames you see reflected in the glass. If all the flames look identical, there is no Low-E coating present. If one of the flames looks slightly clearer and is a different color or hue from the other three, that indicates a Low-E coating. Then, you just determine which flame that is and that indicates what surface the Low-E coating is applied to. See below:

Now that you know whether you have Low-E windows or not, you can consider the window film solutions that may or may not be a good fit for your application. In many cases, windows in northern, colder climates will have Low-E applied to surface 3 to prevent the heat on the inside from escaping out in the Winter. Conversely, windows in southern, warmer climates will have Low-E applied to surface 2 to prevent heat from the outside from entering the into the space in the Summer. In many cases, window films can be used to improve the performance of these Low-E windows. It should be noted though that when the Low-E is applied to surface 3, there are restrictions surrounding what types of films can be applied.

If you have any questions on the information on Low-E windows contained in this article, please contact us by calling 800-234-6133 or emailing us at We would be happy to assist you in answering your questions and also give you the contact information for a local Geoshield installer in your area. You can visit our dealer locator by clicking HERE to find a Geoshield Window Film Authorized Installer in your area.