Hi Summer,

First, tell your contractor that his suppliers are full of pupu (and not the snack variety). Impact windows are not the same as "other laminated glass windows".

I don't generally discuss specific manufacturers, but I do have a few thoughts to share concerning impact windows and their performance...and maybe a couple comments on the systems used by a few different manufacturers...

As you know, impact 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 wont 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 doesnÂt 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 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 donÂt 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 SGPÂs 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 arenÂt strong enough to take that forceÂwhile 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 longevityÂmy opinion only, but I wouldnÂt use it in my house.

Most window manufacturers buy their laminated glass from a laminated glass manufacturer (which does make sense!)Âbut a few laminate their ownÂsuch 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) Â but thatÂs 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 isnÂt 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 homeÂpotentially violently. This can be avoided by placing the lami inboard.

A continuation of yesterday's reply:

I had to go off and do some not-related-to-answering-window-questions-on-the-internet stuff before I finished my answer - and of course the previous answer was way too long anyway...

Concerning the weight versus double hung availability issue, nope, weight is not a problem at all (unless you have to install these things, and then weight becoem a very real consideration!)

Impact glass is heavy, and it can be a real workout to handle it, but the hardware suppliers and the window manufacturers can build products that can easily accomodate the additional weight. The real reason that double hungs are scarce among Dade County suppliers actually relates directly to the Dade testing requirements and procedures.

There are primarily two testing protocals being used currently for impact product certification - Dade County and ASTM E1886 & E1996 - and while the two different protocals are very similar, there are some differences as well - differences that directly affect the certification of double hung windows.

Both protocals require that impact resistant products be able to withstand the impact of an 8', 9lb, 2x4 at 50fps, but Dade County requires impacts to the meeting rail of single and double hung windows and ASTM does not. This difference is huge and it is the reason why single hungs are commonly offered as impact resistant to Dade County Standards while double hungs are rare...it is much more difficult and expensive to engineer and to build a double hung that can withstand a meeting rail impact - and still operate (which is the requirement) - than it is to build a single hung that meets the same requirement.

In addition, double hungs and single hungs are relatively less common than are other styles of windows in the areas that require Dade certification, so it really isn't economical for window companies to invest huge amounts of money into developing a double hung for those areas, although there are cerainly exceptions.

There are some very good double hungs that have not been tested to Dade requirements, yet would probably be more than adequate for your environment. But, if you want "Dade windows" then I would suggest checking out the Dade County list of certified products to see who all makes a double hung that fulfills that requirement.

Good luck in your search and please let us know how it goes!

Oberon, thank you sooooooo very much. It is so kind of you to share this kind of detailed information. I was able to have a more "informed" discussion with my contractor this afternoon, enough at least to get him to give me the detailed list of what I need so I can follow up on the leads you gave me.

I still can't figure out why a custom builder on Kauai, where we had a class 5 hurricane come aground in 1992, isn't more enthusiastic about this. He doesn't seem to think the cost difference is worth it -- he is offering milguard 3050 doublehungs for $266 and I'm guessing that I'm going to be looking at least three times that for impact resistant. (And I neeed 46 of those......) I think he thinks I'm being paranoid, but how can we tell when the Pacific is going to get El Nino again?

Anyway, I will definitely keep you posted with what I find out!

Summer
P.S. Totally off topic, but I'm also grinding my teeth over the local electric company telling me it isnt in their interest to have too many people with PV systems. We have absolutely NO rebates or incentives for installing any sort of PV system. It's absurd in a state where the sun is for free!!

You are very welcome.

I was curious which island you were on. Kauai is beautiful!

People in the Gulf Coast resisted upgraded codes - similar to south florida requirements - for a very long time. Even people in the Florida panhandle were exempted from the "hurricane codes" that were in place in the rest of the state.

Those same folks now have something of a different opinion of those codes. LSU did an assessment of Katrina damage and they determined that 85% of non-flood-related storm damage would have been prevented if the same codes that south florida now requires would have been in place in the gulf where Katrina came ashore.

Does it cost more to protect yourself? Yep, it does. Is it paranoid? Ask the folks in Florida and along the gulf coast their current opinion.

Ultimately, I would suggest it truly is a "pay now" or "pay later" argument...I think you are 100% correct...and I also think that in this area you are much more of an "expert" than is your builder.

You can expect to pay roughly double for the hurricane windows, at least that's the difference for Andersen's Stormwatch units. Most regions requiring impact glass test 3 units with the 2x4 tests oberon mentioned. Each unit receiving 1 strike. In Dade County, each unit is struck 3 times. After being struck, the units are loaded into a pressure chamber, and cycled through 9000 positive and negative pressure cycles, in an attempt to breach the unit. Most hurricane damage is caused by the building envelope being breached, either by broken windows or blown in doors. Once the building pressurizes, it usually blows the roof off.
The other side to hurricane rated windows is Design Pressure ratings, which is what seperates these from regular laminated windows. They usually require installation with steel jamb clips, and have restrictions on joining units together.
Additional hardware may be required to meet the requirements, so be prepared for sometimes a visual impact. Andersen's Stormwatch double hungs come to mind.
Plywood can sometimes be used in a pinch, but if it's not applied properly, it's going to become a projectile. And it blocks egress windows.
If you can afford the protection, you'd be well served to get it. The double hungs operate just fine, but are heavy to carry or lift into an opening for installation.
Good luck with your project!

I've also been considering replacing my existing windows with the impact windows. I live in Ft. Myers, FL and have gotten serveral bids and with varying prices and conflicting info. My questions are:

1. Have been told vinyl is better than alumn. when dealing with impact glass and building code; also the vinyl has longer warranty. Can you shed any light on this matter?

2. Also have been told I don't need to worry whether windows meets Energy Star Ratings because impact glass is thicker than regular window glass and will provide me with energy savings. Is there any truth to this info.?

I figure if I'm going to pay the ridiculis amount of money they want to replace my windows I don't mind spending a little extra for Energy Star Rating if it will truly provide extra savings on the electic bill. I want to make sure I'm doing whats best for the house and our budget. Thank you for any thoughts you may have regarding this matter!

I'm not an expert, but I've learned a few things during the process of choosing and buying my windows.

First, as far as the vinyl versus aluminum question, the only windows that meet the Dade County impact resistance code are the aluminum ones. The vinyl ones meet other standards, but not the Dade County one. I don't know about the warranty issues, but you could probably find the answer to that by looking at the websites for the bigger companies (Simonton, PGT are the 2 I researched the most, oberon above mentions others).

Second, some of my windows turned out to be Energy Star compliant and others weren't. I have huge overhangs from the deck so it wasn't a huge issue with me, except for the tax savings that come from buying ES rated items.

You might want to check with you home insurance company, to see which set of standards are going to get you a break on your insurance as well.

I had a difficult time with my window order, but it had to do with the distributor, not the manufacturer. You might want to actually email some of the manufacturers yourself with your questions, and see what they say.

Hope this helps a little!

Sorry Lady , there are vinyl windows meeting Dade regs. Go to the Florida building code website and do a little research,