"It seems it has an impact point but it’s tiny."

It was enough to crack the glass.

On an impact window the exterior pane of glass is not laminated. The interior pane is the laminated pane. The exterior pane is usually tempered (or annealed in this case) and is considered the sacrificial pane, with the interior laminated pane actually protecting the structure.

Do you have any pictures of the crack?

Impact windows should be built as millworkman described, and most are, but not all. Some manufacturers do build their impact products with the laminated glass outboard rather than inboard often related to whether the window is interior or exterior glazed.

Per your description, I wonder if you do have a window with the lami outboard (exterior) since you describe it as looking like a windshield crack; an apt description for impact glass since it's basically a windshield on steroids.

@oberon476, pics are above (in the vote boxes for some reason) and looks to me like annealed cracked but I may be wrong.

@millworkman I was wondering what that vote thing was all about. I even opened one of them, saw the label, and closed it without noticing the crack. Thanks for the heads-up!

I agree that is definitely an annealed crack. Using annealed laminated is pretty common in impact windows, although some window manufacturers do prefer heat strengthened or tempered laminated, but no question that's annealed glass.

oberon, I am pretty much out of the loop on residential as far as glass makeup. I was unaware that the lami was used by some guys for the exterior lite or that you straight annealed was even allowed for the exterior pane. We do everything tempered, even when it is not required, just precautionary and easier to order it all the same and not worry when you have multiple piece the same size on a commercial job that the right glass gets on the right hole.

If I was building an impact window I would always use either annealed or heat strengthened lami interior and at least 4mm tempered lite exterior. My guess is that is the most window manufacturers do it that way (excepting the 4mm), but I do know of exceptions. Annealed or heat strengthened are allowed for the exterior (or interior if the lami is outboard) monolithic lite, but if I am building an impact window, I am using tempered glass.....and if I am buying impact windows, I want the mono-lite to be tempered.

In my experience most, but not all, window manufacturers want to adhere the laminated glass lite to the fixed stop in the sash, so lami to the interior is a no-brainer for an exterior glazed product, but it can be more of a mixed bag for interior glazed products. Some folks adapt to not sticking it to the fixed stop in that case and build it lami inside, but some need the rigidity of the fixed stop so build it lami outside in that case.

I don't like tempered lami in most applications, especially railings where it's often required by code now, because if the tempered glass breaks on both sides of the interlayer you end up with something with the rigidity of a wet towel. Whereas when built using either annealed or heat strengthened the laminated glass retains at least some structural rigidity in the event of glass breakage. Using SentryGlas mostly alleviates the "wet towel" rigidity problem, but SG is a lot more expensive than PVB and not really necessary for most residential applications.

Thanks oberon, most all my experience the last 15 years has been with commercial and in storefront or curtainwall were are outside glazed 98% of the time, so it is always tempered outboard. That all makes sense. Some of our guys do not like tempered lami as the glass tends to crack and run a bit easier that annealed lami. And exterior applications we always use the SGP interlayer.

I am curious how much laminated you use in your commercial projects and also where it usually comes from.

We use a decent amount of lami, we do a considerable amount of railings and a lot of the medical use lami for the interior partitions. We buy from Old Castle, Press Glass, Viracon, Blue Star to name a few. Smaller projects we have other guys we can get from. Mostly SGP from what I am aware.

We seem to be a little off topic, but we are keeping this thread open until (if?) the OP returns, so that's a plus. Thanks for the info, always great to learn new stuff!

Like wise. I always learn from your posts. Your knowledge of glass is a great resource.