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Impact (or “hurricane”) windows are made with laminated glass, upgraded hardware, upgraded frames and other components, and all sealed in place with some of the strongest silicone (or other) adhesives on the market.
Virtually all the major window manufacturers have impact products available. Some perform extremely well, others barely get by.
Laminated glass is simply two (or more) lites of glass bonded to a plastic interlayer for strength. Laminated glass is no stronger against breakage than is the glass it is made of. Let me say that again - laminated glass breaks as easily as the glass it is made of. I mention that because many folks have the mistaken impression that laminated glass / impact windows won’t easily break. They will break, but the glass adheres to the plastic interlayer and keeps the envelope of the home closed.
There are four major food groups in the impact glass world (a few other minor ones as well) relating to the interlayers used to manufacture the laminates.
First we have PVB or Polyvinyl Butyral. This is the stuff that is in the windshield of your car. It is relatively soft and very flexible, yet it is also tough and doesn’t tear easily. This is probably the most widely used product in the impact glass market since it does great when impacted. It stops whatever hits it and stretches to absorb the impact (such as a persons head in a car accident). PVB is a good product and is the choice for many manufacturers.
The second interlayer type is a hybrid of PVB with a layer of PET film between the PVB layers. This is a very tough product and it performs very nicely, but it can be a problem to manufacture and this product seems to be phasing out of the market – although a number of window companies still offer it.
The third type of interlayer is called SGP or Sentry Glass Plus. This is quite a bit different from PVB in that it is very stiff and very tough. It is becoming something of the product of choice in some of the toughest applications (including some bullet and bomb resistance applications). It is also a bit more expensive than PVB and may be overkill for some residential applications – but I think it is ultimately the best product on the market at this date.
SGP is also becoming the product of choice for a number of the wood window manufacturers, although vinyl folks don’t seem to be using it quite as much yet, but SGP seems to be growing in the vinyl market as well. One reason it is a little behind in vinyl windows is because SGP’s rigidity tends to transfer an impact force to the frame of the window rather than absorbing the impact as does PVB. Some (but not all) vinyl windows simply aren’t strong enough to take that force…while some vinyl windows do quite well with SGP.
The fourth product line is the resin laminates – where a liquid resin is poured between two lites of glass and allowed to cure. I see liquid resin laminate as the “mom and pop shop” of laminated glass – although some larger manufacturers do use it. For the manufacturer it is cheap, it is easy, and it is an acceptable “mom and pop shop” product. Personally, I am not impressed with performance or longevity…my opinion only, but I wouldn’t use it in my house.
Most window manufacturers buy their laminated glass from a laminated glass manufacturer (which does make sense!)…but a few laminate their own…such as PGT (whom you mentioned).
Among the major residential laminators (who are not window makers) are Cardinal, Old Castle, AFG, Arch Aluminum, Viracon and a few others. Of the bunch, Cardinal is almost entirely residential where the others mentioned are generally split between residential and commercial – most being primarily commercial.
As a window company, PGT laminates most of their own glass and they are very good at it. They also outsource some laminated glass as well. Simonton currently buys their laminated glass from one (or more) of the vendors that I mentioned, but I believe that they are in the process of building their own line.
PGT is primarily an aluminum window manufacturer. Their windows have done very well in the past few Florida storm seasons. I believe that they are by far the largest seller of impact windows in the southeast (and probably everywhere else) – but that’s a guess.
When buying IG (dual pane) windows, some manufacturers place the laminate to the exterior, and some to the interior. This is often based on how the window is glazed. The manufacturer wants to seal the laminated glass to the strongest component of the window / sash. Generally this is the "fixed" stop versus the removable stop.
If the window sash is "internally glazed" meaning that the removable stop is interior, then the laminate will be the exterior lite. If the window is "externally glazed" meaning that the removable stop is external, then the laminated glass is likely the inboard lite.
This isn’t 100% though. Some manufacturers prefer one version to another for other reasons – such as keeping the laminated lite inboard to stop broken glass from coming into the home when the “other” lite is broken. If the non-laminate is to the interior and the laminate is impacted, then that other lite will break and the glass shards will be inside the home…potentially violently. This can be avoided by placing the lami inboard.
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