It might seem like a strange question but as I was sitting in my chair earlier this afternoon I heard a noise on my window which I thought might have been a ball or something hitting my window, as one did the other week. I didn't rush outside but a few minutes later went and there were no children about which means nothing as they might have run away having hit my window, it does happen. Then shortly afterwards I heard a noise again, again went out but no children again. Then I was on the telephone just now and looked at the window and could see a curving line, peeped through the blind and saw that I had curved crack about eighteen inches or so.

Now, my question to you is is it possible that a blow to the outside pane of glass could cause the inside pane to crack? If not, what could cause the inside pane of glass to crack?

That unit isn't new, in fact it is quite old and the seal wasn't brilliant, I do get some condensation and it also gets full sun in the afternoon and today it is nice and warm out there.

Thanks.

Did just the inside pane crack, or were both the outside and inside panes damaged?

If the glass or frame is a tight fit, expansion due to temperature can cause cracking, either from the glass itself or the surrounding fixture.

There is some info. here that may give a clue.

http://www.cwct.co.uk/facets/pack08/text06.htm

We are not talking of a new unit here, it has been here since before Imoved here which is more than 14 years. If it was the frame then it would have happened before now.

The sun is on it during afternoon, but that hasn't changed. The temperature inside the room is 27C so probably much the same as the outside temperature.

As I said, a couple of weeks ago a football hit the window, hit by a child so not very strong.

Sue, it is possible that the stress caused by the continues expansion and contraction of the glass over the past 14+ years finally caused it to crack. Glass is a unique material in that it is not solid, it is fluid, and this comes with its own complications and quirks. Different types of glass behave in different manners as well...tempered v. not tempered, plate v. float, etc. Older glass was made using different combinations of raw material than more modern glass. All construction materials from woods, to metals, to concrete and glass expand and contract to varying degrees with temperature change. This constant expansion (with temperature increase) and contraction (with temperature decrease) cause fissures/cracks/breaks in all kinds of materials over time. That's why concrete and asphalt roads crack, why wood floors and walls creak, and why sometimes glass cracks. It's a similar principle to how you can break a paper clip in two by repeatedly bending it back and forth.

My best guess, if only the inside pane broke, and the glass is in direct sunlight each day, that the reason for the crack is the release of built up temperature-related stress in the glass, and that it is just "odd timing" that it happened today. It is, as you know, not always the same temperature outside, and even as a double panes window, the inside pane experiences "relatively drastic" temperature swings throughout the day and year.

I would have said that the inside pane gets far less change in temperature, outside it varies from below freezing to hot whereas the inside temperature is fairly constant.

Oh well, I guess that I will have to contact my insurance company to see if it is covered, if not then the glass people.

The two sides of the inside pane do experience different temperatures, though. While the temperature of your house remains the same, the temperature of the glass still goes up and down. And the air temperature on the inside surface and the outside surface (the part that "touches" the air between panes) are also different temperatures. Even in double-pane windows temperatures of the actual panes change more than you might think.

Definitely do talk to your insurance company, though. It certainly can't hurt anything

A football hitting the frame could have slightly distorted it enough that 14 years of stress became a more relavent variable and a few days after that impact, a crack appeared to relieve the stress. I would look on the outside of the window frame for cracks evident in the frame's paint finish. Any warping or wracking due to the impact would show as a break in the paint finish. Most double paned windows have a gas (Argon?) as the filler atmosphere between the two panes. A fix would require a new window unit and not merely a replacement pane. Without the insulating gas, the window will act like a single paned window which, since glass transfers heat energy quite readily, will act almost as well as an open window rather than a temperature barrier it is designed to be.
Edit: However, the mention that you saw condensation in the window suggests that the gas was long ago replaced with humid air and that the window hasn't been the barrier it should have been. That long ago event which caused the gas to escape the inner space may also be the source of the near cracking stress placed on the inner pane all these years. It may have been a manufacturing defect too. Did you have a 25 year warranty on the unit?

Hope you can get it fixed, Sue.

I don't even know of anyone that has double glazing. We have an English girl working here with my son and one of their school things was to design a model of an energy efficient house .. she couldn't believe that there's not many places with it here. :p

I didn't live here when the windows were fitted and I meant 24 years, not 14, the units were not brilliant even then. There is no evidence as the frame is aluminium and natural metal finish. There would be no mark on the glass as my window cleaner came on Saturday morning and washed them.

I phoned my insurance company and they are submitting a claim so someone will contact me in the next couple of days then come to look at it to see if they will cover it.

The man phoned and told me to get a couple of quote but not to tell the companies that it is an insurance claim as they tend to load the quote! Once I have the quotes to phone him and he will come and get me to sign the form.

It looks as if they might pay up which would be nice.

Well, the main thing I've gotten from this discussion is that I didn't in fact know what double-glazing was. I had figured it was the same as having double hung windows, but it's not even close.

I have wooden single hung sashes, myself, that I have to put a fixed storm window over in winter, and a screen over the part that opens in the summer.

I would have thought that Canada would be all over double glazing!

I think in Russia they have triple glazing from what I can remember.

Agony, double glazing is a sandwich, glass, a vacuum, glass. It is sealed to keep the vacuum and reduces heatloss and sound.

I have had my two quotes, one knew that it was an insurance job, the other I said that I was paying, one was for £718.04 and the other for £524.97. Guess which one I am using.

It also, as I know from experience, offers some protection from hurricane-force winds. During the Great Storm of 1987 I was living in Brighton and the winds were busily uprooting all the trees, stripping tiles off the roof, and generally causing mayhem. One of my neighbours was having some building work done and had had a pile of shingle delivered the day before - the storm picked the pile of stones up and chucked it down the road, smashing car windscreens, and breaking the windows of every house. Except mine - I had double-glazing and the stones broke only the outer pane of glass leaving me still safe and snug inside. Of course I still had to get the windows replaced but as I also had to have a lot of new roof, a total respray of my car, and a bunch of other repairs the new windows barely made the insurance company blink.

I had an email from the more expensive one saying it was a typing error and they knocked off about £180 - but still dearer. I just realised the expensive quote was before sales tax, so even more!

This is a good link to the article at Wikipedia.
http://en.wikipedia.org/wiki/Double-paned_windows

They say the useful expected lifetime of a double paned window is 15 to 25 years. Please note that there is no vacuum between the panes. During manufacture, that space is evacuated and then back filled with an inert, insulative, dry gas. There is mention in the article that some mfr's are now using a descicant in the space in addition to assembling the panes entirely in that gaseous atmosphere so they don't have to drill holes for the evacuation and backfill. A vacuum would put a constant strain of 1 Atmosphere on both the inner and outer panes while the backfill gas reduces that strain to zero and lengthens the expected useful life.

Both of the men coming to measure up were of the opinion that the crack was most likely to be the result of a blow to the edge of the frame, neither offered an opinion as to the likelyhood of it being a stress crack. Neither said anything about cracks sometimes 'just happened'.

We have double paned windows in our house, plus two triple paned. There is no vacuum between the panes, as mehaul says. However (in ours) there is no gas either. The spacer is either foam or aluminum (or a combination of both) which reduces fogging and heat buildup (I know that might not make a lot of sense, but it does for insulation r value). In some double glazed windows the spacer is filled with a dessicant (again, not a "gas" per se) to reduce fogging. Am fairly certain some of the windows in Agony's house are double paned (unless she lives in a farmhouse older than 50 years). In 30 years, we have only had to replace one double paned window due to a broken seal (because our dog tended to "stand" on the inside piece of glass on the "sidelight" door window and bark at strangers who came to the door lol - which would equate to a "blow" of some sort as sue said). If you have any sort of break in the sealant (between or outside the panes) it can result in either the inner or the outer glass having an "injury".

And further, contrary to Kaddersgirl's opinion, glass is NOT fluid. It has no viscosity in its final form. Scientists have have even dispelled the idea about stained glass in churches being thicker at the bottom as pure myth as far as 'flowing' goes. It's more a matter of how the glass was made in the molds in the first place. And in any case, the types of glass used "today" (with all their different "additives") are nothing like the first glass created on earth (which um, would be lightning striking sand) ... : )

Jakeroo...

First, I said nothing about glass in windows being thicker at the bottom because of movement in the glass over time.

Second, I mentioned that there are different types of glass which are all made differently (I believe I mentioned plate, float, tempered...).

Third, technically glass is an amorphous solid, which has a disordered, non-crystalline structure (similar to fluids), which is different than most "solids", though it does exhibit solid behavior under impacts. And that is NOT an opinion.

Fourth, this was dealt with and Sue got her answer weeks ago. And even though the crack in her glass was determined to be the cause of a blow to her window, does not mean that in other cases there are not other reasons for fractures. I have seen fractures that have nothing to do with impacts.

Considerably older than 50 years, yes.

And, really, I don't think I've ever seen the windows described. I have tended to live in older places, though.

Wow kgirl, didn't know you were a glass blower like me : ) I prefer that talent to growing a chip on my shoulder (at my age, I can't afford any more bone deterioration lol)

Despite your perplexing reaction, this is the only part of your message I disagreed with and I will quote it here :

"Glass is a unique material in that it is not solid, it is fluid".

Um yup, it certainly is when you're making it, but not as an end result. Not even so-called "float glass", which refers more to a process rather than a product. Regardless of what you googled, the term amorphous is a bit of a cop-out since the different types of glass - OVER HISTORY - make it wishy-washy to put in one category or the other). Nothing with viscosity would be used to make WINDOWS (especially in our climate, in THIS century). Go ahead and edit it out of your original message if you want lol. I couldn't care less.

And unless you're a moderator as well as a chemist/glass expert, I really don't think you have the right to determine whether a response from ANYone at ANYtime is "out of date" or not : )

Ah, Agony. You make me pine for my gramma's old house in Saskabush! Double hung windows with sashes and 3 holes for "ventilation" : )

Sue: glad the trouble appears to be "sorted" and that you seem to have gotten a fairly good price : )

Yep, those are the ones. Out on a ladder every spring and fall changing out the storms and the screens.