Have you heard of SentryGlas? If not, you might want to read on, because the U.S. Department of State’s (DOS’s) Bureau of Diplomatic Security (DS) used it to replace the glass clad polycarbonate (GCP) that it once relied on to protect diplomats in countries abroad from things like guns and explosions.
What is SentryGlas? Why is the Bureau of Diplomatic Security changing from GCP to it? Can you, as a private homeowner in Florida, get similar-quality protection for your own home?
Let’s find out!
What Is SentryGlas?
SentryGlas, originally created by DuPont Glass Laminating Solutions in 1998, SentryGlas is a lamination solution that is stated to be “100 times stiffer and five times more tear resistant than PVB and, in addition, exhibits the highest post-breakage strength over a broad range of temperatures and loads.”
In other words, it’s an extremely strong glass laminate solution that is ideal for resisting impacts without breaking or tearing.
DuPont Glass Laminating Solutions, and by extension, SentryGlas, was acquired by a Japanese company named Kuraray back in 2014. So, SentryGlas is now a Kuraray product.
PVB, or Polyvinyl Butyral, is itself a strong type of plastic film commonly used in hurricane impact windows. The PVB interlayer joins two pieces of impact glass together and acts as a shock absorbing layer in windows. PVB made for architectural applications has a tensile strength of roughly 25 megapascals (MPa), or over 3630 psi, and a shear modulus of 14 MPa, or 2030 psi, (Source: MatWeb), though this can vary depending on the manufacturer’s formulation.
In comparison, SentryGlas has a tensile strength of 34.5 MPa (5003 psi) and a shear modulus of 77 MPa (11165 psi) at a temperature of 104 degrees Fahrenheit over the course of a full second (Source: Curbell Plastics).
While the tensile strength and rigidity of SentryGlas aren’t quite “100 times” greater than PVB, the difference between the two is rather notable. If you take a sample of PVB and a sample of SentryGlas in hand, the PVB will have a notable rubbery texture, flexing somewhat easily with a little pressure from your finger. Meanwhile, the SentryGlas laminate will be much more difficult to flex with a single finger.
Here’s a quick comparison. Here’s a sample of PVB glass being pressed with a thumb:
Here’s a different sample with a piece of SentryGlas:
Here, you can clearly see a difference in how much the material flexes. The PVB sample flexes easily while the SentryGlas sample barely budges.
Why Did SentryGlas Replace Glass Clad Polycarbonate in DS Architecture?
So, why did the Bureau of Diplomatic Security change out its old GCP-based ballistic resistant glazing for windows and doors with options using SentryGlas?
The Bureau of Diplomatic Security’s memo noted that they were looking for a GCP alternative that would “not de-laminate and would not require SpallShield on the interior surface for glass spall prevention.” Prior to making the change to SentryGlas, the DS had noted that “Physical delamination of GCP products is a phenomenon that has been well-documented.”
SpallShield is a secondary product that was noted as being “relatively expensive” by the DS and “once damaged or scratched, SpallShield cannot be repaired or replaced in the field.” So, it was an extra expense on top of the expense of getting another layer of material on the interior of the glass beyond the GCP itself.
With the SentryGlas solution, the Bureau of Diplomatic Security had a product that it could rely on to withstand extreme impacts from firearms and near-miss explosions to keep diplomats safe in extraordinary situations. That’s why it replaced glass clad polycarbonate.
What’s Spalling?
Spalling typically refers to a break in a material. However, in the context that the Bureau of Diplomatic Security uses the term, it’s referring specifically to the ejection of glass shards from the “safe” side of a window when the glass is struck with a fast-moving object (such as a bullet).
If the glass spalls violently, then the glass shards themselves might become a hazard to the person or persons standing behind the window. Preventing spalling is one of the key reasons why the DS changed from the GCP products to SentryGlas-based ones.
SentryGlas is much more rigid than PVB or other materials. Because of this, it doesn’t flex as much when struck at high speed. This minimizes the risk of glass spalling on the side of the window opposite the impact side.
Can I Get SentryGlas for My Windows?
So, if you’re a security-conscious homeowner who wants the maximum possible protection for your home, is SentryGlas something you can get for your windows and glass doors?
Actually, yes. You can get SentryGlas for your home’s windows and doors. Two of the top window manufacturers in Florida use SentryGlas in their top-of-the-line HVHZ window and door products… They just give it different names.
Simonton Windows calls the window option that uses SentryGlas Safepoint Max+. This is their impact glass protection solution for HVHZ-rated windows and sliding glass doors that is made slightly thicker than their standard glass.
Meanwhile, PGT has an option to upgrade their window glass that they call the SGP interlayer. This is an optional upgrade from the standard PVB interlayer that their impact windows typically use.
You can request an upgrade for your windows to have them use SentryGlas. However, there will be a premium for using it compared with the more standard PVB interlayer.
Is SentryGlas Worth the Added Cost?
It depends on what is most important for you as a homeowner. If you want the peace of mind of knowing that your windows are practically unbreakable and use a material that the U.S. government employs to protect diplomats from threats, then upgrading to an HVHZ-rated window or door that has SentryGlas might be worth the extra cost.
There’s a certain amount of prestige that comes with being able to say “and my window glass is the same kind of glass that they use to protect diplomats.” It’s also nice to know that your windows are rated to stand up to Cat 5 hurricane conditions without breaking a proverbial sweat.
However, if your primary goal is just to meet Florida Building Code (FBC) requirements for replacing windows in a wind borne debris (WBD) region, then standard impact windows with the PVB interlayer are more than sufficient to meet your needs. Full-on HVHZ windows might be a little overkill for your needs.
Does Karoly Windows Install SentryGlas-Equipped Windows?
Yes! Karoly Windows & Doors does installation work on HVHZ-rated products that use SentryGlas through Simonton and PGT.
To ensure that your windows are as strong as possible, we perform every installation with our own in-house team of experts. This is something that set Karoly apart from many other window companies that just sell you the windows and farm out the actual installation to the lowest-bidding subcontractor they can find.
Expert installation by dedicated professionals helps ensure that, when you choose HVHZ-rated windows, no corners get cut. This, in turn, helps ensure that your windows are as strong as possible to stand up to hurricanes and other threats.
Looking for SentryGlas-equipped windows and doors for your home? Reach out to Karoly Windows & Doors and ask us about HVHZ-rated windows for your home!
