"jay" wrote in message
news:un9Md.10893$8a6.5021@trndny09...
Fatigue due to thermal stresses in glass is cumulative.
This is about pyrex, but the same principles apply:
http://www.newton.dep.anl.gov/askasc...9/eng99265.htm

Ok, so I guess this means the other panel in the adjacent window could be
on the verge of damage, right?

Even though I removed the window film, I'm thinking that perhaps the
double-cell honeycomb shades (with side tracks) are a big part of the
cause. Today it's sunny out, and if I pull down the shades for a while,
and then lift them up and put my hand on the window glass it gets hot, and
VERY hot toward the top 1/3 of the glass (can't even keep my hand on the
glass)

The glass did NOT get that hot when using the levelor aluminum blinds that
came with the condo. The glass got warm but not hot.

Do you think I'm risking another crack by continuing to use the insulated
shades, given that they cause the glass to get very hot?

One key point: these shades have side tracks to seal the edges, which
causes hot air to get trapped between the shade and the glass.

My goal, when getting the shades was to prevent heat from getting into the
room. This "worked" but not I have a cracked glass panel. I could remove
the side-tracks, or go back to using leveler blinds, but that would mean
I'll have to live with the room itself getting too warm.

Again, do you think it's okay to use the shades as is, even though they
are causing the glass to get very hot? I find it hard to believe the
window film alone was the cause of the crack. The shades have to be LEAST
50% of the cause. (the tinted window film was not very effective at
keeping heat out of the room)

J.

it is always better to prevent the heat from getting inside. once it's
inside, it has nowhere else to go and you have to pay to move it outside.
use outside shades, trees, or even sunscreen on the outside of the window to
solve your problem.