Thank you. Thank You. THANK You! I will keep note of which I see it more in, as much as possible, (DH, and DTAB helped dig and store them, and I couldn't keep up with both of my helpful guys ðÂÂÂ) I am off to read up... KateQ

Glass isn't going to crack due to a light piece of cardboard lying against it. My theory is that solar storms, which have been very active lately, caused an increase in the hyper and hiper-frequency range of radiation. This cause huge spikes in not only the delta but also the alpha frequencies. Glass is normally very stable under normal cosmic bombardment. However on this day, the huge spiking caused the radiation to pass through the glass and instead of reflecting back into a less dense atmosphreric vortex, the cardboard cause a build up and the glass molecules became unstable causing the glass to break.. This is obviously a case of a glass manufacture ignoring peer reviewed technology, readily available for the asking and IMO shows almost a complete contempt for consumer safety. What would have happened if a child had been close and the cardboard not muted the effects? We would be talking about more than just a mere glass fracture. This demonstrates a very high level of disregard for common public safety and as such a lawsuit should be certain. Let us know how it works out.

At negative 10* outside, I can't imagine much that would heat that window to the point of being "hot". There could be some heat reflection, etc, but again, I wouldn't think it could reach that threshold given exterior temps. Ultimately, if nothing hit the glass, the crack will have sprouted from an imperfection on the egde of the glass, which could be sparked by extreme temp differences. Much like when a crack sprouts from a chip in your windshield in the hot sun. I will say though that your installer's level of suspicion is likely due to the shape of the crack. Most stress cracks are pretty smooth and linear, and do not have sharp turns like that which could indicate some sort of impact. Not saying that is the case, just what is most often observed,

We have run into the exact same problem. We have a newly remodeled fireplace and used the Kingsman ZRB46 gas fire place insert and a ceiling to floor marble slab surrounding it. Our contractor and stone fabricator assured us this would look striking and there were no foreseeable problems. Our marble splintered immediately after first use in several places and has since been torn out. The contractor and fabricator believed its from the heat expansion of the fireplace and with the correct modifications and using a harder stone, that we can still retain the striking seamless look we were after. My doubts are high on this. Can you suggest a better idea to surround this type fireplace? I don't want to waste more time and money. Thank you for your help.