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Melting Vinyl Siding: Causes and Solutions

In recent years, homeowners have increasingly turned to low-E (low emissivity) windows for their energy efficiency benefits. These windows are designed to reflect heat, keeping homes cooler in the summer and warmer in the winter. However, a surprising issue has emerged: melting vinyl siding.

This phenomenon has raised concerns among homeowners and has significant implications for property maintenance and safety. It has also caused us to take phone calls about our reflective film to see if it will cause a similar phenomenon. In this blog post, we’ll delve into how low-E windows can cause vinyl siding to melt, what signs to look out for, and what you can do to prevent it.

Understanding Low-E Windows

Low-E windows are coated with a thin layer of metal oxide that reflects infrared light while allowing visible light to pass through. Like solar control window film, this coating helps reduce heat transfer, making these windows effective at improving a home’s energy efficiency. However, the reflective properties that make low-E windows so desirable can also create unintended consequences. 

How Low-E Windows Cause Melting Vinyl Siding

The melting of vinyl siding occurs when low-E windows reflect and concentrate sunlight onto a specific area of the siding. This concentrated reflection can generate temperatures high enough to distort or even melt the vinyl.

This often happens when the sun is lower in the sky during the Fall and Winter months – which may be counterintuitive to folks.

Here’s a closer look at the process:

Reflection and Concentration

Low-E windows are dual pane windows. When heated, the pressure from the gas between the glass can cause the exterior pane of glass to become concave. This can result in the glass reflecting sunlight in a focused manner, similar to how a magnifying glass can concentrate light to create heat. When the angle of the sun is just right, this concentrated light can be directed onto a small area of the vinyl siding.

Heat Generation

The concentrated sunlight can cause the temperature of the vinyl siding to rise dramatically. While vinyl siding is designed to withstand typical weather conditions, it can start to deform at temperatures above 160 degrees Fahrenheit. The intense heat generated by the reflected sunlight can easily exceed this threshold.

Siding Deformation

As the vinyl siding heats up, it can begin to soften and warp. In extreme cases, the siding can melt completely, leading to significant damage that requires repair or replacement.

How Close Do Low-E Windows Have to Be?

The million dollar question is, how close do the windows have to be to cause damage?

The proximity of low-E windows to the vinyl siding plays a crucial role in the risk of melting. Typically, the closer the windows are to the siding, the higher the risk of concentrated reflections causing damage. The specific distance at which this occurs can vary based on factors such as the angle of the sun, the orientation of the house, and the type of low-E coating used on the windows.

Some sources don’t want to give a number, but others say that generally, homes where low-E windows are installed within 20 feet of vinyl siding are at higher risk, especially if the windows face directly towards the siding.

Signs Your Vinyl Siding is Melting

Homeowners should be aware of the signs that indicate potential damage to their vinyl siding due to low-E window reflections. Key indicators include:

Warping or Buckling

Noticeable distortions in the siding’s shape, such as warping or buckling, are common signs of heat damage.

Shiny or Glossy Spots

Areas of the siding that appear unusually shiny or glossy may have been subjected to high heat levels.


Fading or changes in color in certain sections of the siding can also indicate exposure to intense reflected sunlight.

Preventing Melting Vinyl Siding

Fortunately, there are several strategies homeowners can employ to mitigate the risk of their vinyl siding melting due to low-E windows:

Use Specialty Window Film

There is a specialty exterior film made to prevent vinyl siding (or turf) from melting. This is not a film that Concord Window Film provides but there are several options in the marketplace. We are providing these examples as a starting point for you to do further research as we haven’t vetted the companies to make recommendations:

Turf Guard

Turf Shield

Install Awnings or Shutters

Adding awnings or shutters to windows that reflect intense sunlight can help block and diffuse the light before it reaches the siding.

Add Exterior Screens

Exterior insect screens mounted on the windows are enough to prevent the concentrated reflection from happening.

Strategic Landscaping

Planting trees or shrubs near the windows can provide natural shade, reducing the amount of sunlight that gets reflected onto the siding.

Replace with Non-Reflective Windows

If the problem is severe and persists, you may have to consider replacing low-E windows with non-reflective alternatives in areas where the reflection is causing damage.

Melting Vinyl Siding Conclusion

While low-E windows offer substantial energy efficiency benefits, they can sometimes lead to unintended consequences like melting vinyl siding. Adding a reflective solar control or privacy window film to your existing windows could potentially also cause melting vinyl siding. By understanding the causes and signs of this issue, homeowners can take proactive steps to prevent damage.

And, although we haven’t had any issues specific to Concord Window Film, if this is something you are worried about, please use the following guideline. If your windows are 20 feet or closer to vinyl siding, we would not recommend installing a reflective window film on your windows.

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