Due to the damage hail causes to aluminum siding, the trend for residential buildings has been to use vinyl siding. It has become more and more difficult, if not impossible, to even purchase aluminum siding. Most aluminum siding manufacturers have either closed or remodeled to produce vinyl siding. At first glance, this seems like a huge trend that could eliminate insurance claims for siding damage.

Due to the cost of energy to heat and cool your home, the trend for residential buildings is to install Low-E reflective windows in all new construction. Due to the recent government energy credit, the trend for residential buildings is to remove existing windows and install new or replacement windows that are also low-e reflective. What Low-E technology does is reflect heat away from cold. Simply, in winter it keeps the heat in and in summer it keeps the heat out.

You may ask, “What does this have to do with my vinyl siding melting?” Across the country there have been mysterious occurrences of vinyl siding distorting, warping, and even melting with seemingly no explanation. In fact, cases have been reported in Connecticut, Georgia, Florida, Illinois, Iowa, Maine, Massachusetts, Michigan, Minnesota, New Jersey, North Carolina, Ohio, Oregon, Pennsylvania, South Carolina, and Washington. If this happens to you, you may be experiencing VSMS, Vinyl Siding Melt Syndrome, or as Owens Corning calls it, Reflective Distortion. Reflected distortion can occur when the sun reaches the perfect angle to deflect from a low-e glass window, being magnified by reflection to a point where the heat produced exceeds the distortion/melting point of the vinyl siding. Manufacturers list this distortion point as the heat deflection temperature. This heat deflection point is generally around 160 to 165 degrees Fahrenheit. Although there have been cases of coating distortion due to sun reflection on non-Low-E windows, it appears to be more common with Low-E glass. Since the sun’s vertical angle with respect to the earth changes from month to month and the sun moves horizontally across the sky minute by minute, this phenomenon has a very small window of opportunity for it to occur.

Conditions can only be perfect on a single window pane for about 1-1.5 hours per day for 20-30 days per year depending on window size, trees, clouds, etc. Unfortunately, this reflection can come from your own window or even your neighbor’s. There are other factors that can contribute to this heat gain. Whether the home was built using aluminum clad siding or Visqueen interior vapor barrier. Aluminum clad siding can intensify heat gain and Visqueen would prevent heat from escaping into the house. On this point, window and siding manufacturers disagree on who is to blame. Neither of them blames themselves, but both seem to be working on a solution.

There are also some issues as to who would be responsible for the damage or the cost to prevent it from happening. Could you be responsible for replacing your neighbors’ siding or would you have to buy new windows or awnings if your windows melt their siding? Since this is an ongoing event and not a one time event, would your insurance policy cover the damage or would you have to pay for the siding replacement? Since this is a relatively new phenomenon, no one has the answers yet. For now, keep an eye on your siding. If you have no problems but your neighbor installs new windows, start taking care of your siding again. Now, if you see that your siding has started to distort, warp, or melt, at least know what might be causing it and the mystery may be solved.