:::::UPDATED:::::
Does the following problem seem fair to anyone? Feeling a little screwed over????
Dwyer glass came and replaced my window under one year ago. When they came there was a black 'beware of dog sign' in the window. The owner of Dwyer Glass, never mentioned it being an issue. Replaced my window. Now the window is cracked and he claims it's from the black sign being in the window made with TEMPERED glass, called it "thermal stress". Although even if that's true the sign was in my previous window for years and it never cracked. And if he new that it would crack my window should he not have said something to warn me???? When I asked him this he said "not my job to tell you these things"!
After the owner left I googled thermal stress and this was the first thing that popped up...
"The quick answer is Yes, a dark vinyl which absorbs heat can cause a temperature difference in the glass. Its called thermal stress fracture.
The cracks will usually be a propagation of a crack which already exists in the edges of the glass from its cutting process. This is because standard Annealed (or Float glass) glass is cut to size by scoring with a diamond tip then snapped. This process causes many tiny invisible cracks along the edges which are usually no problem. However any of these cracks can potentially propagate at any time. The risk is increased by various factors such as size of the pane, exposure to the sun, shading of part of the glass by an overhang or tree but it can just happen spontaneously because the pane was installed slightly at an angle and it is just settling in the frame. So glaziers follow guidelines so as to reduce the risk of this happening. Notice I say reduce as there is no way of guaranteeing it.
This is with Annealed glass.
Toughened (TEMPERED or Heat Treated) glass however is very unlikely to suffer from this as each piece is made to size (rather than cut) and the heat treating process seals the edges removing all these cracks. Also as the glass has been heated to a far higher temperature than you would expect from solar absorption alone then again it is unlikely to crack unless already damaged" -Stuart Miller, Glass Pro