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Hurricane Windows: Five products that will work for you

Source Post: http://www.replacement-windows.com/windowbb/viewtopic.php?p=2390

Good thread.

Jonchaley, you are after the best of both worlds. Basically, if you want hurricane protection, you want laminated glass. If you want sound abatement, you want laminated glass. How easy can it be?

Actually, it gets better. For maximum sound attenuation (deadening) you also need a tight, heavy window sash and frame. It really doesn't matter how good (or expensive) the glass is if the frame is not up to the same standards. But, when you buy an impact rated product, you are buying an entire window unit that has been tested and certified to some rather stringent requirements and the window systems is about as tight as a window system can be.

There are five basic types of impact (hurricane) products available currently....windows made with any of these systems can have DP ratings of 45 and upwards. Commercial and some residential windows made with the stronger materials have DP ratings well over one hundred.

First, is polyvinyl butyral or PVB. This is the same stuff that is in the windshield of your car, only the PVB interlayer is either .090" or .100" thick versus the PVB layer in a windshield is .030" thick.

PVB does a very nice job of sound blocking and is generally the product of choice when designing for sound.

Second, a few companies offer the PVB with a sheet of PET film sandwiched between two layers. This product is a bit stronger than ordinary PVB, but it is also quite a bit more expensive.

Third, some laminators offer a product called SGP or Sentry Glass Plus. This is a .090" interlayer that like PVB is laminated between two lites of glass, but it is about 100 times stiffer and has about 5 times the tear resistance of PVB. But, this product is costly. Many of the major window companies offer an SGP option, but often it is an upgrade for really large windows. This product is used extensively in larger commercial windows because of its resistance to stress due to its stiffness.

Fourth are the liquid resin laminates. A number of companies offer these products in Florida (and somewhat elsewhere). The difference in these versus the previous three is that the PVB and SGP are sheet goods laminated to the glass using a pressure and heat system.

The resin products are liquids that cure either thru chemical reaction or else by exposure to UV light.

Several of the resin laminators also use a sheet of PET in their product for additional strength.

Finally, are the glass / plastic hybrids. These are generally a sheet of Lexan (polycarbonate) laminated between two layers of glass using a urethane to bond the materials.

These units are incredibly strong, but they have a tendency to distort in high heat / sun because the polycarbonate has a different coeficient of expansion versus the glass.

As I said, all of these options are available to you in Florida. There are also the aftermarket films, but I didn't mention them for several reasons...I will say that they offer no sound advantages and leave it at that.

STC, or Sound Transmission Class is the measurement used to determine the ability of a window (or wall or door) to attenuate sound...that's the simple part. Unfortunately, it becomes a bit more complicated.

I am going to offer a few examples, but please bear in mind that there are other factors affecting the sound performance of a window besides just the glass.

A single sheet of glass has an STC of 30. Simple as that. But, below about 250hz, the specific sound transmission loss of 21db or decibels. At 2000hz, that same lite has a transmission loss of about 35db. See the relationship? Although the overall is STC 30, the sound performance of the unit is best at 2000hz. After that, the performance starts to decline.

As humans, we are born with the abilty to hear from 20 to 20,000hz. By the time we are teenagers, we have lost the ability to hear much over 14,000hz.

We hear low frequency sounds best. Low frequency sounds travel the furthest (notice the base on kid from down the street's stereo as he drives past your house?)

So, notice that the poorest performance of the single lite is in the lowest part of the spectrum?

When constructing an IGU (Insulating Glass Unit) for sound abatement (beyond the normal), the manufacturer will do one or more of several things.

They will increase the width of the airspace, they will make the two lites in the IGU of different thickness, and/or they will use laminated glass.

I have to run off for a bit, so I will add more to this later.

Source Post: soudn proof windows
http://www.replacement-windows.com/windowbb/viewtopic.php?p=2390
Posted: Fri Mar 25, 2005 9:01 pm