Important Protection in Hurricane Zones
Windows that are marketed as hurricane-resistant or storm-proof are constructed with impact-resistant glass treated with a layer of polyvinyl butyral (PVB) or ethylene-vinyl acetate (EVA). While impact-resistant glass will probably still shatter upon strong impact from flying objects, it generally remains attached to the inner membrane and the window frame. When they break, these windows crack in a fine, spider-web pattern rather than sending out flying shards of glass.
In addition, ordinary windows can be made more resistant to shattering by adding a surface membrane that covers the window glass. This improves the shatter-resistant quality of the window, though not to the same degree found in genuine hurricane-resistant windows.
Genuine hurricane-resistant windows are expensive, at $40 to $55 per square foot, but they can be in good investment in regions prone to very strong winds.
Like any standard window, frame construction on a hurricane-resistant, storm-proof window can use aluminum or steel, vinyl, or wood. Aluminum or steel frames are considered the strongest (and most expensive), but there is some maintenance associated with these. Vinyl-framed windows are a great cost-effective solution with good insulation value, but at the end of their life, recycling the materials can be difficult. Wood frames offer good insulating value, but because they need to be regularly painted, the cost of maintenance is highest among the three frame options. And over time, wood windows can be susceptible to warping.
There are also several glass options when it comes to hurricane-resistant, storm-proof windows. The different glazing types are identified by the laminate procedure by which the glass panes are joined with the interlayer.
- A film of PVB (polyvinyl butyral) or EVA (ethylene-vinyl acetate) sandwiched between two layers of glass is the most common type of hurricane-resistant window. PVB or EVA does a very good job of absorbing impact when struck. This layer of PVB or EVA typically ranges from 0.015 to 0.090 inch thick, with thicker layers increasing both the price and the strength of the windows. PVB is the same film that is used to make car windows shatterproof.
- PVB combined with a layer of PET (polyethylene terephthalate) makes for a very strong glazing option, but due to a challenging manufacturing process, these windows are also very expensive. These windows often consist of two layers of PVB-treated glass with a PET film between them.
- Another option is SentryGlas Plus (SGP). In this technology, created by DuPont, an interlayer of proprietary inoplast material sits between panes of glass. SentryGlas is lighter in weight, stronger, and less susceptible to yellowing over time than other storm-proof options. The SGP layer is roughly 0.90 inches thick. These windows are more common for commercial windows, though they can be ordered for residential purposes. They are among the most expensive of hurricane-resistant windows. SGP is also used where bomb- or bullet-proof glass is required.
- Liquid glass resins can be permanently applied to glass by a process that uses UV light as a catalyst to cure and harden it. In some versions, a PET film is also added to make the glass even stronger. Liquid glass resin windows are especially popular in Florida.
- Glass/plastic hybrid windows sandwich a thin sheet of polycarbonate Lexan between two panes of glass and bond the materials together. This results in a very strong glass, though the product is not a good choice for very warm climates since the polycarbonate tens to expand more than the glass.
Hurricane-resistant windows are also available in a range of thermal options for use in different climates.
How Hurricane-Resistant Windows Protect in Storms
You might expect that the main advantage of non-breaking hurricane-resistant windows is that they prevent water from damaging the inside of your home, but the real advantage is structural. Studies have shown that total home destruction is often caused by the sudden pressure changes that occur when windows and doors blow out entirely. The increased air pressure entering the home can blow off roofs and cause walls to collapse. Keeping the windows and doors intact and preventing these air pressure changes can save a home from a devastating collapse.
The call for hurricane-resistant windows hit full stride after Hurricane Andrew struck Florida in 1992, causing an estimated $25 billion in damage. In response to this, certain hurricane-prone areas have adopted new ASCE (American Society of Civil Engineers) guidelines for windows in new construction. Beginning in 2001, new homes in Florida and some other at-risk areas were required to be built with either shutters or hurricane-resistant windows to make the structures less susceptible to total collapse.
To carry the designation as hurricane-resistant, windows must be able to meet certain requirements for surviving impact from both large and small missiles. The large-missile test involves hurling a 6-foot long 2 by 4 weighing 9 pounds at 50 feet per second in laboratory conditions. The window glazing and framing must remain intact after the impact. The small-missile test involves hurling 30 pieces of grave or steel ball bearings at 80 feet per second—again, the window must survive in order to meet the standards.
Hurricane-resistant windows are aimed at helping a house survive a storm with 200 mile-per-hour winds (Category 5). When buying windows, look for models that are approved for the standards required by the building code in your region.
The Energy Conservation Code also requires that impact-resistant windows must have a maximum U-factor of 0.75 or less and a solar heat gain coefficient (SHGC) of 0.30 or less.
Hurricane-resistant windows can increase your overall construction cost, but they offer great protection during the storm season. The investment may well pay for itself by preventing storm damage, and it can also allow you to qualify for discounted homeowner’s insurance rates.
A good hurricane window, including frame and glass, will cost between $40 and $55 per square foot of glass area. Some studies have shown that by installing hurricane windows, the construction cost is increased only by a few thousand dollars on a new home.
As an average, a hurricane impact door size 60×80 inches can cost about $1,900 while a sliding window 72×80 inches is around $1950. An average single-hung window costs between $500 and $600, materials only.
If you’re thinking about getting hurricane windows, the following advantages and disadvantages can help you make your decision.
- Windows are made to break safely and survive very strong winds
- Provides sound insulation and protects interior by blocking UV rays
- Can reduce homeowners insurance rates
- Can add several thousand dollars of extra construction costs
- Adds unnecessary costs in areas without severe storms
- Some types yellow over time and have imperfect visibility
No glass is entirely break-proof, but hurricane-resistant, storm-proof windows have the enormous advantage of breaking in a manner that cracks without sending out flying shards of glass. Some of the many benefits of impact-resistant windows are:
- Will survive winds up to 200 mph without blowing out
- No flying shards of glass
- Available in different styles and sizes
- Offer excellent insulation against sound
- Blocks 99% of transmitted UV light
- May reduce homeowners’ insurance costs by as much as 45 percent.
- The high cost can add several thousand dollars in construction costs on larger homes.
- An unnecessary expense in regions where severe storms are unlikely.
- Glass can yellow on some types over time.
- Visibility can be slightly reduced on styles with thick glass.