Problems and Controversy
It has been determined that low-E windows are the culprit of melted vinyl siding installed on nearby houses and buildings, with initial reports of such damage surfacing in 2007. This is because the intense heat reflected by the windows can be focused, similar to the burning effect that can be achieved by focusing the sun’s rays through a magnifying glass.
The problem generally occurs when the sun strikes a low-E window and the reflection lands on the side of a nearby house, causing its vinyl siding to become hot enough that it melts and distorts. It has been reported that the hot glare can affect siding up to 20 feet away. The melted siding usually exhibits a diagonal pattern across the distorted area.
The intense reflection from low-E windows is reported to have caused other kinds of damage, as well, such as melted plastic trash bags and plastic garbage cans, melted plastic solar collectors, melted plastic parts of vehicles, and melted housewrap on new builds yet to be covered with siding.
Four house fires were confirmed to have been caused by such reflections, according to an investigation by the Consumer Product Safety Commission. In these cases, reflections from sunroom roof glass and skylights ignited nearby cedar shingles.
The hazard is not limited to property. One new high-rise hotel in Las Vegas reportedly gave off reflections hot enough to burn people using the hotel pool.
Windows with standard glass panes can cause similar damage in some situations, but this is rarely reported.
Who Is to Blame?
There has been some controversy and debate about this, focused mainly on whether the manufacturers of the windows or the manufacturers of the damaged siding should be held accountable. Representatives from both industries have been tight-lipped about the issue, and neither party admits liability. Some representatives have tried to downplay the issue, stating that damage to siding caused by low-E windows is an extremely rare occurrence. At the same time, every major vinyl siding manufacturer has updated their warranties to specifically exclude heat damage caused by window reflections, implying that the problem may not be nearly as rare as industry representatives contend.
At least two organizations, the Vinyl Siding Institute and the American Architectural Manufacturers Association (a window-makers' association) have begun research on the problem but have not released any findings. It is likely that as awareness of the problem spreads, more data will be gathered and eventually made public.
As the debate continues over who should be held accountable for damaged siding, forward-thinking manufacturers are looking ahead for ways to deal with the issue. One solution that vinyl siding manufacturers have begun to implement is an additive that can increase the vinyl’s resistance to heat. The additive, called TempRite™, is manufactured by Lubrizol, a chemical company specializing in polymers and resins, and known primarily for their CPVC plumbing pipe. Siding manufactured with this additive can withstand temperatures in the range of 225° F, while traditional vinyl siding will begin to warp and distort at around 170° F.
Other more simple solutions have also been suggested, such as planting bushes or trees to shade siding from the windows' glare, or using awnings and shades at the window to help minimize the windows' strong reflections. While these may not be effective solutions long-term, and don't address whether the manufacturing process of low-E windows should be altered to prevent their hot reflectivity, they can be helpful in the meantime while the problem and potential solutions are being researched.
As low-E glass becomes more common, inspectors are likely to encounter it more frequently. Knowing something about how it works and the controversy surrounding it will help inspectors answer clients’ questions about low-E glass during home inspections and energy audits.