With increased attention on cases of siding distortion, we’re committed to addressing concerns homeowners, builders, remodelers, architects, code officials, or the media. Below are answers to some of the most common questions about siding distortion.
Damage to property caused by concentrated sunlight is infrequent and occurs only under a unique set of conditions. Homeowners can protect their personal property in such instances by blocking the path of sunlight, either to the window or between the window and the siding. This includes the strategic placement of trees, bushes, or other landscaping elements and the use of sunshades above windows. Screening applied to windows may reduce the total amount of reflected energy and help to avoid the problem.
The chances of siding distortion occurring on any given house are extremely small. Vinyl siding is the most popular choice of exterior cladding, and has been for about two decades. There are tens of millions of houses sided with vinyl. Only a tiny percentage of those houses have been affected by exposure to concentrated sunlight reflected from windows.
A very narrow set of conditions needs to come together in order to cause the problem, and this happens very infrequently. If your house has not been affected in the past, it is not likely to be affected in the future. This can change, however, if windows are replaced (either on your home or your neighbor’s) with ones that are more likely to concentrate the sunlight, or if something that blocked sunlight is removed.
It is not possible to predict what distance is at greatest risk or whether there is a “safe” distance from the window. This is a topic of on-going research. The range or “zone” of distance from the window in which the reflected beam is most concentrated depends mostly on the curvature of the glass. The curve can be different for different windows, and can even change in the same window under different temperature and atmospheric pressure conditions.
No. Other materials can be raised to temperatures known to cause short-term or long-term damage from exposure to intensely concentrated sunlight. Anything that falls in the path of that reflected beam can be harmed including cups, bags, pool covers, car parts, painted surfaces, and cedar shingles are a few of the materials reported in the media to have been damaged. People who have found themselves in the path of such beams of have reported extreme discomfort and the inability to remain exposed for more than a few seconds without enduring the risk of burns. Eye damage from even a brief exposure is highly likely.
No. The ignition temperature of vinyl siding is approximately 720-750 °F (380-400 °C). This is well above any temperatures reported to have been caused by even the most extreme cases of concentrated sunlight reflected from windows. In fact, the ignition temperature of wood is lower than that of vinyl siding, so wood materials such as siding, fencing or decking would be at greater risk of ignition than vinyl siding.
When vinyl siding is distorted by the heat, the vinyl siding is changing shape, but does not break down or release toxic chemicals at the temperatures reached in reflected sunlight cases. The combustion and other conditions necessary to create dioxin do not occur with reflected sunlight.
No, the thickness, color, or “quality” of the siding are not likely to be major factors. Many of the conditions that affect the risk of distortion from concentrated sunlight are still being studied. Concentrated reflected sunlight has caused distortion of light and dark siding, and even the thickest and most expensive profiles. These factors may make relatively small differences in the occurrence of distortion, but their effects are overwhelmed by the large amount of energy transmitted in a beam of concentrated sunlight. Effective solutions must involve preventing the windows from concentrating the reflection, or by intercepting or diffusing the beam before it strikes the siding.
No. Based on current laboratory research and field observation, there’s no evidence that the nature of the underlayment has a significant effect on distortion.