Patching the glass will not be a complete repair. The vaccuum between the two glass panes has been lost. It will require a factory-sealed unit.

Ah, I hadn't thought of that. Lovely. Well, I do appreciate your pointing that out. Thanks.

AND, it might not be just a 'vacuum', but the space
between the panes might be filled with some inert gas,
which only means one thing .... 'MO MONEY' to replace.

There is no vacuum between the glass, just plain old DRY air.
Since the airspace is there to insulate, a vacuum wouldn't do as good a job.
Call a re-glazier or two and get a quote. It may eventually fail and show dirt/condensation between the panes, but probably not right away.

"Since the airspace is there to insulate, a vacuum wouldn't do as good a job."

Wrong, wrong, wrong. A vacuum is the ultimate insulator.

Thanks to everybody for weighing in. I'm not having any luck with finding a window person who will address the problem--everyone is, of course, trying to sell me windows. I live out in the country and no glazier appears too motivated to come out here to examine the patient.

I still wonder what the product may be to try just filling in this starburst crack--I can't determine whether the entire pane of glass is penetrated. I'd settle for less than perfect if I could simply fill in a bit of the starburst without making the whole thing worse.

Thanks!

Glass a glass shop, they specialize in replacing glass and will change it no problem. They also may be able to tell you if it is worth repairing or it it actually needs replacing.

I just had the same thing happen in an upstairs room of our farm office. Is this what yours looks like? I can't see how this was caused by a rock given its placement. The crack originates below the sash or frame of the window. To me it looks more like a stress fracture but the company said it's not. The window is less than 2 years old. It's going to cost me $240 plus mileage to get it fixed. I think they're replacing that section of the window - he said he could do all the work from the interior. Only the exterior pane is broken.

I've toured several window factories and no vacuum pumps in sight.

I received an email challenging my post about the vacuum. It is difficult to create an envelope to contain and maintain a vacuum and thus many manufacturers use other methods to deal with the space between panes on double glazed windows.
A couple of semesters of college physics will show the superiority of the vacuum-- but that is beyond the scope of this forum.
Most field repairs of double glazed windows just capture ambient air between the panes.

Hilltop, that's a dreadful crack! I have a hard time seeing how that's not a defect in the window....but anyway, no, mine is much much smaller, just about an inch across...just a smack from a rock.

Hope it gets fixed to your satisfaction. Wish mine could.

Jumpilotmdm, bus_driver is correct. A vacuum is the best insulator but it is usually cost prohibitive so the next best thing is a noble gas (eg. argon), followed by just plain dry air.

"the next best thing is a noble gas (eg. argon),"

It is not the noble nature of the gas that is useful here, it is its ability to transfer heat.

As the selaed glass industry found out a while ago with less effective seals, differential leakage on sealed units (the pure gas inside leaked out faster than the atmospher could leak in) they inadvertently did create a vacuum.

Many of these units then bowed the glass panes inwards, and a few even explode (tempered glass units) when the glass could not take the stain of bending.

The office building we rent has had a couple failures this way.
It sounds like a soft boom and one side of the units glass is instantly reduced to 'crumbs' of tempered glass (so far they have actually stayed in place until touched for removal).

Non tempered glass usually just cracks at a weak spot and the atmosphere rushes in.

A vacuum would be better than anything (the way a Thermos flask or Dewar flask works) but you need to deal with the 14.7 PSI of atmospheric pressure loading the glass panels.

Not that hard on a cylindrical shape, very hard on a flat panel.

The gas fill is 14.7 PSI f the desired gas so there is no physical loading of the glass, and a standard pressure gauge would read zero pressure between the inside and outside (even though one side is an almost pure fill gas and the other is the atmosphere).

Sorry, I didn't mean to imply that all noble gases are good insulators, it's just that the two gases that I know are used in double pane windows happen to be noble (argon and krypton).

Those gases happen to be less expensive and poor at moving heat.

There are others that would be even better, but they are many times more expensive IIRC helium would do a great job, but is VERY hard to contain.

It actually leaks through the walls of steel gas cylinders (slowly, but it leaks).

Agree. Typically argon or krypton, usually argon. Vacuum would be great, but glass would need to be very thick. Most of these windows have (or should have) a one-way pressure relief valve to allow some of the internal gas to escape if the pressure is too great. I've even heard they make special "high altitude" windows so they don't pop.

OP, here's a thought: is it the fixed portion, or the opening portion? If the opening portion, then remove it and take it to the glass people. Much cheaper.

If fixed, you will have to get them in. You really should bite the bullet and get it done, no half-assed home repair is going to work.

Glass is breached, you'll get moisture inside. Pretty soon, everyone in the house will cease to care, old cars and trucks will litter your front lawn, dogs and cats will start living together...

Plus, winter's coming. Your heating bill will be a bit higher.

alan s thefirst, alas, its the fixed portion.

I don't actually think that the glass has been breached. We'll see. Its a very small injury to the outer pane.

My post seems to have prompted a lively, and to me unintelligible, discussion about gases. I'll let ya'll know in a few months whether there's fog or no fog.

Already got that dog / cat consorting going thing on in my house, so I suppose its all downhill from here.

There is dessicant in the spacer between the two panes. The purpose of the dessicant is to absorb moisture that make sits way into the cavity space. The sealed unit is there to prevent/minimize any moisture from getting into the cavity space and condensing on the interior surfaces of the glass.

It is my understanding that the effects of the filling the cavity with air versus a specific gas are negligible for all practical purposes (of course manufacturer's will debate this as the gas filled units are more expensive).

There is avery often an air exchange between the cavity and ambient air but as long as moisture is held to a minimum then fogging won't be a problem. It is the air space created by the cavity that provides the vast majority of the insulating value not vacuum or the specific gas.

OP: If you need to reapir the broken pane and you're "out in the country" you might contact a glass place, explain the situation and ask if the window can be disassemebled by the homeowner so that you can bring the just the insuklated glass unit (IGU) to the shop and get a replacement.

If we are allowed, we end up learning and learning. I was told about the gas from a window mfg., so the actual truth might be something different. A vacuum never made sense to me, even considering the thermos thing?
I'll bet you're fogged by 2 changes of seasons. I was also told the dessicant is only for the few moments of exposure during the mfg. process. At the time it made sense. After all this above, I'm not so sure.
And I think dogs & cats living together is a good combination.

"Glass is breached, you'll get moisture inside. Pretty soon, everyone in the house will cease to care, old cars and trucks will litter your front lawn, dogs and cats will start living together"

One of the funniest comments I've read on GW. Thanks for the laugh alan_s_thefirst!

Hope you find some help to fix the glass shadygrove. I've had a window with a small single pane starburst fracture for years btw. 0o. :)

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