Vinyl Siding – Can Your Home’s Replacement Windows Cause it …

A mysterious phenomenon seems to be plaguing homeowners-their vinyl siding is warping and buckling, or as some describe it, “melting.” The Vinyl Siding Institute as well as the National Association of Home Builders both insist that the problem is not widespread. However, the complaints have attracted enough media attention lately to cause some concern-and Low-E energy-efficient windows have been taking the heat.

The charge goes something like this: because double-paned, energy-efficient windows “bow inward,” the concave shape focuses the sun’s rays like a magnifying glass. Temperatures, consequently, can reach over 200 degrees Fahrenheit. When sunlight bounces off these windows, they say, vinyl siding can literally melt.

But are double-paned, energy-efficient windows really the culprit? There are other explanations for such warping. Even homebuilders are reluctant to blame the neighbor’s windows, and point to a variety of factors that could affect the intensity of the reflected sunlight. In fact, they recommend that each case be investigated on an individual basis. To quote the National Association of Home Builders, “The use of double paned low-e windows will not necessarily result in any damaging reflected sunlight incident. A combination of contributing factors must be present before the effect occurs….”

I’ve also discussed this with a local home inspector, who agrees-there are other contributing factors that can cause vinyl siding to warp, buckle and melt. He’s observed it mostly in newer neighborhoods, where the construction of homes is congested and concentrated, so homes are really close to one another. Plus, reflected and radiant heat can come from a number of sources, not just windows:

  • pavement
  • roofing
  • some underlayments
  • and of course, direct sunlight!

And just maybe it’s the siding.

According to current manufacturing standards, normal grade vinyl siding begins to distort at 160 – 165 degrees. That’s pretty low! Especially when you factor in atmospheric conditions such as wind speed, air temperature and seasonal sun angles. Now add to that the proximity of your neighbor’s windows…

Second, what lies under the affected siding might be contributing to the problem. What was installed underneath it? For example, if an interior vapor barrier was installed behind the drywall, heat will build up inside. Add reflected heat to the equation, and well, you see the problem…

But have you heard the saying, “Cheap is the most expensive price to pay?” What is happening here just may be more indicative of cheap siding, and to some extent, cheap thermal pane windows. Inferior products just can’t be trusted to hold up under extreme conditions.

True, if the glass on a window is sucked in, it can form a veritable parabolic dish, which condenses and concentrates the heat waves, much like a solar stove. But if the siding is thin enough (and close enough), after prolonged periods of sun exposure at the right angle, it can droop.

One solution is to choose better siding (one that is under warrantee for more than a year!) Look for heat-resistant vinyl siding that can withstand heat ranges of 185 to 220 degrees Fahrenheit. Choose your product carefully and discuss how the siding will be installed with your contractor or homebuilder. How thick is this siding? What will be under the siding? Is there another, more durable product that I can buy? What’s new on the market? What’s covered in the warranty? And remember-cheaper can end up costing you more!

Local building codes all over the country now require energy-efficient windows to be installed, and for very good reasons. Low-E glass technology and energy-efficient construction make good sense for your home and for the environment. So energy efficient, double-paned windows are not going away anytime soon. All new building products manufactured these days need to be of the highest quality and durability and designed to be compatible with one another to ultimately protect you-the consumer.

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