Can you install window film on double-pane windows?

The short answer is yes! You can install window film on double-pane windows, but there are some important considerations to keep in mind.

What is a double-pane or dual-pane window?

Double-pane windows, also known as dual-pane or double-glazed windows, are windows made with two panes of glass separated by a layer of air or gas. The two panes of glass are typically separated by a spacer, which creates an insulating barrier between the two panes.

The space between the panes of glass can be filled with air or an inert gas, such as argon or krypton, which has better insulating properties than air. This insulating layer helps to reduce heat loss during the winter and heat gain during the summer, making double-pane windows more energy-efficient than single-pane windows.

Double-pane windows can also reduce outside noise and increase security, as they are more difficult to break than single-pane windows. They are commonly used in residential and commercial buildings to improve energy efficiency and comfort.

What is thermal stress?

Thermal stress is a physical phenomenon that occurs when an object is exposed to temperature changes. When an object is heated or cooled, its molecules expand or contract, causing the object to undergo thermal expansion or contraction. This can create stress within the object as different parts expand or contract at different rates.

Thermal stress can be particularly problematic in materials such as glass, which have low coefficients of thermal expansion. This means that they expand or contract relatively little in response to changes in temperature. When such materials are exposed to rapid temperature changes or to extreme temperature differentials, they can experience significant stress, which can lead to cracking or even fracture.

Thermal stress and windows

Thermal stress in windows is typically caused by changes in temperature. When a window is exposed to a significant difference in temperature between the interior and exterior surfaces, it can cause the glass to expand or contract at different rates, which can lead to thermal stress.

For example, during the day, sunlight can cause the exterior surface of a window to become much warmer than the interior surface. At night, the opposite may occur, with the exterior surface becoming much cooler than the interior surface. If these temperature changes are significant enough, they can cause the glass to expand and contract, which can create thermal stress.

Can you install window film on double-pane windows?

As we mentioned before, you can absolutely install window film on double-pane windows if:

• You choose a window film made for double-pane windows
• You evaluate the condition of your double pane windows to make sure there aren’t any factors that could contribute to thermal stress

Choose a film made for double-pane windows

First, it is important to select a window film that is suitable for use on double-pane windows. Some window films may not be compatible with double-pane windows, and it is important to check with the manufacturer to see if the film you are considering is suitable for double-pane windows.

All ComforTech™ Ceramic Series films are approved for use on double-pane glass less than 40 square feet in size.

Films that cause excessive heat on a window that is in an area with large temperature swings, can lead to rupturing of the window seals (the units will fog up) or to glass breakage due to thermal stress. This situation is well known to the entire solar film industry. Films that absorb much of the solar energy rather than reflect it are more susceptible to causing this type of failure. Often these are the very light-colored films. In general, films that have an absorption percentage of greater than 50% are typically not recommended for dual pane windows.

You can see in the chart below that all ComforTech Ceramic Series films have a total solar absorptance of 50% or less and are appropriate for double-pane windows:

Evaluate for other contributing factors

There are other factors that can contribute to thermal stress:

• Windows that are already damaged, chipped, or cracked
• Poorly designed or installed windows that do not allow for proper expansion and contraction of the glass
• Direct exposure to hot or cold air currents, such as those created by heating or cooling systems
• Shading of a portion of a window, but not all of the window
• Single glass panes larger than 40 square feet

Concord suggests that you evaluate your window conditions before purchasing any window film by using our handy guide to determine if your windows are a good fit for window film.

Summary

The appropriate window film can be installed on double-pane windows that are in good condition and don’t have any contributing factors. If you live in an area of the country that doesn’t have fast temperature swings, this is less of an issue. If you have temperature swings, always check the manufacturer information to make sure you are purchasing a double-pane compatible film, and take a look at your window conditions using our guide linked above to see if any exist. When in doubt, choose a window film with a total solar absorbtance rate of 50 or less.

But its important to note that thermal shock and seal failure occur even on windows where no window film has been applied.  Less than 0.1% of all windows in the United States have window film applied to them, yet windows can and do break every single day.  This means that 99.9% of all windows that break don’t have window film as the cause.

To learn more about ComforTech™ Ceramic Series window film for your double pane windows visit our website: www.windowfilm.com.