Warped vinyl siding

Does anyone know what might cause vinyl siding to warp or bubble? It is just one stud space. The interior side of the wall is an unheated garage.


Do a message board or google search. This has been discussed here several times.


May be reflective rays from high e-glass neighboring windows, BBQ grill, etc. These windows appear to be this type.

reflection from the window, if you replace the siding it will likely happen again.

Solar reflection, like Ken said, from the window.

Here’s a more recent link.

That explains it. The window does face south. Thanks for the help.

Unless they tint the window causing the problem.

BTW: PVC reacts it IR energy more than it does to “heat” (temperature). So if your wondering when it get’s too hot to do this, it doesn’t.

PVC fabrication is done with light, not heat… (but heat is present with this intense light, but not required).

That just sounds so wrong, David.

Didn’t you ever start a fire with the magnifying glass. That’s the effect of the light off the glass window. Heat! Don’t believe me. Find one of those areas when it’s actually got light refracting on it and measure the temperature of the vinyl.

Tinting the window may void its warranty and/or damage the window.

solar screens
simple savings solution won’t void warranty

solar screens
simple savings solution won’t void warranty
apply to the culprit or all windows
those in the sunny/hot states already do this for comparatively inexpensive energy efficiency
“good neighbors” have been know to split costs as both benefit in the end, ymmv

Okay, I was trying to keep this in as simplistic a form as possible.

Have you ever seen a PVC pipe bending tool?

It utilizes a lightbulb to generate infrared light which softens the PVC so it can be bent. It does not rely upon the light to produce heat, rather infrared energy which does not burn the pipe material. The lightbulb generates energy in the IR spectrum rather than generating heat within the box.

#1 PVC is very reactive to infrared radiation.

The “magnifying glass” analogy is not at all similar to what is going on here.

A magnifying glass allows all of the electromagnetic radiation of the sun to pass through the lens, that warps and focuses the radiation to a fine point at the proper focal one. The result is a light so bright you can hardly look at it!

On the siding scenario there is no such concentrated focus of light and heat. It is reflected off of the flat surface of the glass and actually becomes diffused and less intense than that coming from the sun. Reflection off of the glass is actually diffused rather than concentrated. The geometry of the reflected radiation further disperses the concentration of solar electromagnetic radiation.

It is perceived that the heat involved in warping the siding comes from the sum of the solar exposure directly from the sun and that which is reflected off of the glass.

If this were the case, this condition would not occur in Alaska and Canada in the wintertime (as it does).

In most cases you cannot even see the solar reflection on the siding when this event occurs.


Again, PVC is reactive to infrared radiation.

Energy in the infrared spectrum is not visible to your eyes, therefore you don’t see it on the side of the house.

Next, electromagnetic radiation in the infrared spectrum does not pass through glass. So a much smaller amount of the sun’s energy is reflected off of the glass while the rest of the energy passes through the glass and heats the interior of the home.

This reflected infrared radiation is absorbed by the PVC siding and the temperature of the siding increases and causes the melting.

My statement that this is IR radiation versus reflected heat was a layman’s explanation indicating that this is not the same as having a barbecue grill up against the siding where the heat generated from the grill melts the siding. What actually causes the siding to melt is energy which is absorbed by the vinyl material, not what temperature it is subjected to.

In this picture you can calculate the orientation of the sun that causes the damage to the siding. The higher up the wall the damage goes, the lower the sun elevation. This shows that the orientation of the sun is low in the sky which would coincide with the winter months in the northern hemisphere. If this condition was happening in the summertime when the outdoor air temperature is high and the sun is intense, the damage would be focused at the bottom of the wall due to the sun’s elevation. As we can see in this photograph, this is not the case.

So the combination of air temperature and reflected solar temperature cannot be supported by these angles.

It would help to know where you’re located Don.
suggest filling out your profile information

All that to say the relection got the siding hot enough to warp?

warping? if you mean its bowed away from house, i’ve actually seen it flex and look correct at different times (my neighbors house), you’d never know as you only see the defect one time. If the product was installed improperly (too tight to building with relly sunk down screws instead of the appripriate nails, or nailed in with gun not in slots provided but through puncture holes, it will not expand/contract with temp changes and bow out, when it gets hotter than instalation temp…

If you mean the vinyl panels have changed shape, i suppose the above scenario is plausable too…it would have to be HOT, only likely in hot areas, not seen up here in RI.

Outside temperature has nothing to do with solar reflection.

Distortion to vinyl siding from reflected sunlight has been reported in all geographic regions where vinyl siding is used.

This effecthas been observed in Minnesota, Illinois, New Jersey, Maryland, Virginia, North and South Carolina, and Georgia.

Understanding Solar Reflection and Heat Distortion

still don’t get it? can you get a friggin sunburn without getting hot? You guys make me wonder more than sometimes…


Apparently he’s never been skiing…good way to fry your face and you won’t know until it’s too late.

Gee, now that is better than the magnifying glass thing! :wink:

At least it applies!