©2015 Green Building Advisor. From The Taunton Press, Inc., publisher of Fine Homebuilding Magazine.
UPDATED September 3, 2013
In almost every corner of the U.S., reports are increasing  of vinylCommon term for polyvinyl chloride (PVC). In chemistry, vinyl refers to a carbon-and-hydrogen group (H2C=CH–) that attaches to another functional group, such as chlorine (vinyl chloride) or acetate (vinyl acetate). siding that has been melted by sunlight bouncing off nearby windows. This melted-siding pandemic makes vinyl manufacturers very nervous — so nervous that the topic is rarely discussed.
Most reported cases involve siding that melts, gets replaced, and then melts a second time. One possible reason for the apparent increase in cases of melted siding is the increasing use of high-performance glazingWhen referring to windows or doors, the transparent or translucent layer that transmits light. High-performance glazing may include multiple layers of glass or plastic, low-e coatings, and low-conductivity gas fill..
Arlene Taraschi, a homeowner in Delanco, New Jersey, described her melted siding in a letter to a Q-and-A column in the Philadelphia Inquirer: “Two years ago, my husband and I purchased a new, Pulte-built home in South Jersey. After a few months we noticed the vinyl siding on one side of the house seemed to be dented in a diagonal pattern. The siding contractor replaced the siding on the entire side of the house. This was done last January, and by February the denting pattern began again. We were told at this time that it was because of the reflection of the sun’s rays from our neighbor’s house. Pulte has termed this melting of the siding ‘thermal distortion,’ and refuses to correct the problem.”
As Taraschi’s case makes clear, these cases aren’t just public relations nightmares — they’re legal nightmares. Arlene’s husband, Carl Taraschi, told me, “I’ve sued Pulte, the siding installer, and the siding manufacturer.”
Since 2007, when I first reported on cases of siding melted by window reflections, I’ve collected homeowner reports of the phenomenon from 16 states (Connecticut, Georgia, Florida, Illinois, Iowa, Maine, Massachusetts, Michigan, Minnesota, New Jersey, North Carolina, Ohio, Oregon, Pennsylvania, South Carolina, and Washington).
Danny Winters works for Cimarron Homes, a builder in Durham, North Carolina. Winters told me, “I think it is a common problem. We are looking for solutions. At one of our houses, the reflection hits the home next door. These are south or southwest facing windows. Whenever I’ve seen the problem, without fail, the melted siding makes a diagonal pattern, starting high and coming across in a downward motion. If you look in communities with a lot of vinyl siding, with houses on relatively small lots, you’ll see that pattern.”
A television news report on the phenomenon from a Boston-area TV station has been posted on YouTube .
According to Dave Johnston, the technical director for the Vinyl Siding Institute, the phenomenon is rare. He noted, however, that “most [vinyl siding] manufacturers have had to deal with the issue.”
One striking piece of evidence that such problems are not as rare as industry representatives maintain is the fact that all major manufacturers of vinyl siding have now changed their warranties to exclude damage caused by window reflection (see the accompanying sidebar, “Vinyl Siding Warranty Exclusions”).
According to a statement released by the Vinyl Siding Institute, “The typical heat distortion [melting] temperature of vinyl siding is approximately 160 to 165 degrees Fahrenheit. When temperatures reach these levels, the siding could distort.”
Michael Bitterice, Albert Lutz Jr., and William Siskos — three engineers employed by glass manufacturer PPG Industries — wrote an article on the phenomenon for the February 2004 issue of Window and Door magazine. The authors reported that dark-colored vinyl siding, if installed in a location where it receives reflected light from a window, can reach 219°F.
According to Mark Haupt, a homeowner in Winston-Salem, North Carolina, sunlight bouncing off a window is hot enough to burn his fingers. Haupt posted this message on a Web forum : “The vinyl on the chimney [chase] … is melting. …This past weekend I was outside at high noon. It was a bright and sunny day. What I saw was the sun reflecting off the window putting a line of high heat — sunlight — about 1 inch wide and about 3 feet long, the length of the melted siding. I could put a finger on the siding and hold it there for less than 5 seconds; it was that hot.”
Glass experts and home inspectors agree on one point: since vinyl siding can be melted by reflectance from conventional clear glass, a low-eLow-emissivity coating. Very thin metallic coating on glass or plastic window glazing that permits most of the sun’s short-wave (light) radiation to enter, while blocking up to 90% of the long-wave (heat) radiation. Low-e coatings boost a window’s R-value and reduce its U-factor. window is not required. Leslie VanAlstine, a home inspector in Dewitt, Michigan, told me that he has seen four examples of melted vinyl siding due to window reflectance; three of the homes had low-e windows, while the fourth had windows with conventional clear glass.
However, the use of low-e (or low-solar-gain) glass appears to increase the risk of melted siding. According to an article in the March 2007 issue of USGlass Magazine, “A study performed by Cardinal on this topic examined the impact of reflective coatings on this type of [vinyl siding] damage. ‘The more reflective coatings that are out there today, that are getting more popular, are going to create this problem,’ [Jeff Haberer] said. However, Cardinal found that even clear glass can become a significant heat source.”
Glass with a low solar heat-gain coefficient has a high solar reflectance. “What we are getting is very, very good windows,” said Jim Petersen, the director of R&D at Pulte Homes. “Now the energy that is not getting in the house has to go somewhere, and it’s being reflected.”
When an insulated glazing unit becomes slightly concave — a phenomenon called “glass deflection” or “collapsed glass” — reflected sunlight can be concentrated. According to Bob Spindler, the vice president of technical services at Cardinal IG, glass manufacturers are aware of the concavity problem but find it hard to eliminate. “The glass manufacturers make IG [insulated glazing] units parallel or as close to parallel as possible,” Spindler told me. “But because of barometric pressure and temperature differences, the space between the panes can become negative.”
According to Tim Singel, a marketing representative at Guardian Glass, there is no simple cure for the problem of vinyl siding melted by glass reflectance. “The issue you are describing is fairly complex, having to do with geometry and building materials as well as orientation to sun, wind and shading,” Singel told me. “There have been circumstances over the years where glass and siding have both been replaced to no avail.”
Most representatives from window manufacturers are reluctant to talk about melted vinyl siding and glass reflectance. Cameron Snyder, a public relations representative for Andersen Windows, told me, “I have heard nothing like that reported about our products.” When I called again and mentioned Kevin Kelly, a homeowner in Parlin, New Jersey, whose vinyl siding was melted by an Andersen window, Snyder said he’d look into it. Later, Snyder provided a few brief comments. “It is handled on a case-by-case basis,” he said. “This is a glass issue, not a window issue, and it is an issue that happens very infrequently.”
Jim Krahn, the manager for advanced research at Marvin Windows, was more forthcoming. “This is something that we have been aware of in excess of ten years,” said Krahn. “If we start with too many recommendations for solutions, then we might be held responsible. We’ll leave it between the vinyl siding people and the glass people to resolve it.”
Among the manufacturers of vinyl siding that have tried to resolve cases of siding melted by window reflections are Alcoa Home Exteriors, CertainTeed, Heartland, Louisiana-Pacific, and Owens Corning.
In Alcoa’s “Field Guidelines For Warranty Claims,” the siding manufacturer notes, “Alcoa … siding will withstand all naturally occurring temperature spikes. Melting will only occur when a window reflection, gas or charcoal grill, or other heating device significantly raises the temperature.” When I contacted several representatives of vinyl siding manufacturers, they all agreed on one point: melting vinyl siding does not represent a manufacturing defect. “Thermal deformation can happen when windows are at an angle to the siding,” Jim Worden, head of Issues Management Communications for Owens Corning, told me. “The siding can actually deform. In the industry, this is not considered a product defect.”
Vinyl siding manufacturers are known to interpret their warranties narrowly; several homeowners have posted messages on Web forums complaining that siding manufacturers ignore complaints about siding melted by window reflections.
According to a recent Journal of Light Construction article  on the melted-vinyl phenomenon, the Vinyl Siding Institute hints “that manufacturers are working on improvements to vinyl siding that would raise its melting point beyond 200°F, but these are still in the development stage.”
According to window manufacturers, the high temperatures caused by window reflectance represent an unusual condition that no siding product can be expected to withstand. On the other hand, some homeowners maintain that window reflectance is a normal condition, so any siding that melts under reflected glare is defective.
These opposing perspectives are cited when different product manufacturers blame each other for melted vinyl siding. As one anonymous Web poster noted, “The siding representative is blaming the window manufacturer, the window manufacturer is blaming the siding manufacturer, and they are both blaming the building designer for placing the window too close to the corner.”
Even when manufacturers or builders are willing to step up to the plate, solutions remain elusive. While some builders may decide to switch to fiber-cement siding or brick veneer, the substitution is costly. The Vinyl Siding Institute suggests three possible solutions: planting a large bush or tree to block the reflection; installing an awning to shade the window; or installing a window screen.
“What we generally do, when people have this situation, is to suggest four or five ways to resolve it — for example, blinds on the window, or plantings like bushes,” said Owens Corning representative Jim Worden. “In some cases we have been replacing the siding, with the provision that they take certain precautions to avoid a recurrence. But no matter what you do, some folks won’t be happy.”
One possible problem with the "plant a bush" solution: there are reports that window reflections can burn plants.
In addition to melting vinyl siding, window reflectance has reportedly damaged other products, including garbage bags, plastic solar collectors, composite (plastic) deck boards, housewrap that hasn’t yet been covered with siding, and plastic rear-view mirrors on vehicles.
Sunlight reflecting off the windows at a new high-rise hotel in Las Vegas has not only melted plastic garbage bags; it has reportedly caused severe burns  to hotel guests sunbathing beside the hotel pool. Now that's a litigation nightmare!
Similarly, in 2013 the windows on a curved skyscraper in London reportedly melted the rear-view mirror and some plastic panels on a parked Jaguar automobile . (In addition to the previous link, check out the following BBC News story: "How does a skyscraper melt a car?" )
Perhaps the most alarming cases of glass reflectance are those involving the ignition of cedar wall shingles. According to the U.S. Consumer Product Safety Commission , reflections from sunroom roofs have caused four house fires. The commission has issued an alert that states, “Sunlight reflecting off of certain sunroom roof glass and skylights onto adjacent cedar shingles or cedar shakes could pose a fire hazard. … Cardinal IG and Four Seasons [a manufacturer of sunroom components] are aware of four fires that could be attributed to this scenario. There are no reported injuries. The damage ranged from minor damage to shingles and underlying sheathing to incidents that caused some structural damage to roofs and walls. … Cardinal IG and Four Seasons working together will repair the roof glass through installation of a capillaryForces that lift water or pull it through porous materials, such as concrete. The tendency of a material to wick water due to the surface tension of the water molecules. tube.”
When I contacted Cardinal representative Bob Spindler to learn more about the recall, he was tight-lipped. “Four Seasons is a customer of ours, and what happened in that case is between Four Seasons and Cardinal,” said Spindler. “There are some things that shouldn’t be published. There are certain things that from a political standpoint one can’t comment on.”
Getting a handle on this problem is made difficult by the fact that data on these incidents are closely held by window manufacturers and the vinyl siding industry. While at least two organizations — the Vinyl Siding Institute and the American Architectural Manufacturers Association (an association of window manufacturers) — have arranged for research on the topic, neither organization made their data public. According to Jery Huntley, the president of the Vinyl Siding Institute (VSI), "VSI would be willing to release the information from the research, as we think it sheds light on the circumstances causing the problem. However, we are contractually prohibited from doing so without the consent of all parties, which has not been forthcoming."
The problem of melted vinyl siding due to glass reflectance shows no signs of going away. “As we build more energy efficient houses with better windows, reflected energy will be a bigger and bigger challenge,” Jim Petersen told me. Petersen’s point was echoed by Danny Winters, who predicted, “With low-e windows now being required by code, there will be a lot more people with these problems.”
Last week’s blog: “Ten Green Building Myths.”