Better than a Crow's Nest: Wonderful Windows

The world is so full of a number of things, I'm sure we should all be as happy as kings!
Robert Louis Stevenson 1850-1894

Learning about windows was a lesson in how one seemingly basic object can have many layers. The word ‘window’ comes from the Old Norse word, ‘vindauga’, from ‘vidr’ (wind) and ‘auga’ (eye). Long ago, someone weary of their dark surroundings poked a hole to let in light and air, and windows were born. Over the next 3 or so thousand years, man has been working to improve on the idea, so that now the simple hole poked in the wall can be framed and covered with materials to let in light but not heat, to be durable and lovely, and to be strong enough to withstand some of nature’s strongest events.

The data hunt began with FEMA’s Mitigation Assessment Team reports. From there, the trail led to the Florida building Code and Miami-Dade Notices of Acceptance and also to the Texas Department of Insurance’s Windstorm Inspection Program. Then, Vince began what he calls “peeling the onion” of information by contacting window manufacturers, reading web-sites, and talking to folks in the window industry.

First, the windows needed to be strong; because window failure in hurricanes has huge consequences. When a window fails under pressure (frames come apart, glass shatters) or is broken by flying debris, the structural envelope of the building can then be penetrated by the force of the storm which pressurizes the interior of the house. At that time, the house is acted on simultaneously by two different forces: 1) the Bernoulli Effect from the exterior, which is creating lift on the roof, and 2) the increased interior pressure, which is pushing from underneath the roof. When the combination of those forces becomes too great, the roof will pop off. If you lose the windows, you lose the roof, and you lose the house.

Window strength is measured as Design Pressure (DP), and is measured in pounds per square feet (psf). Windows can be engineered to meet various DP ratings, based on environment and usage. Design Pressure is the contemplated force per unit area that a surface is expected to see in operation. The total expected load for the surface can be obtained by multiplying the design pressure by the total surface area. In a hurricane, a window needs a certain DP to be able to withstand the force and pressure of the storm. Higher wind speeds mean higher pressures. This is a separate criterion from withstanding impact from flying debris. Increased DP requires thicker glass, a stiffer frame, and limited window size in given situations. (p.s. When testing for DP, engineers include a 1.5 safety factor, so a window that is sold as a DP 65 actually passed the testing for DP 97.5.)

Impact glass is laminated glass. It consists of two sheets of glass with an inner shatter-proof membrane between them. Different interlayers and thicknesses provide different levels of response to storm loads. This page from the Solutia web-site offers a great explanation for impact glass: http://www.keepsafemax.com/pages/ShowFile2.aspx?id=113 Our windows use Dupont’s Sentry Glass Plus and not Solutia, because SGP has a lower yellowing factor than the Solutia glass, but Solutia is an excellent product and often used by our window manufacturer.

It has been interesting to realize that most everything can be measured and quantified and that there are whole groups of people whose work it is to do that. For windows, there are many more things to be measured than one might imagine. The four big considerations after DP and the impact rating are Solar Heat Gain Coefficient (how well the window blocks heat from sunlight), Low U value (how well heat escapes through a material), UV Blockage (how well the window blocks the sun’s ultraviolet radiation), and Visual Transmittance (how well the window can be seen through). Additionally, it was important to find out how the specs were reached, exactly what materials are used for each piece, how those were tested, and what long term issues have been discovered. (Sometimes the laminate interlayer can yellow, or the gas fill can leak). This gets to be a bit mind-numbing, especially when each value is represented by a number and each component has a chemical.

Here are the specifications we started with for the windows:

General: The windows requested are impact resistant design for a coastal oceanfront application in a high hazard hurricane zone. Therefore, all windows must be certified to meet all requirements of either the Miami-Dade County Building Department Approved Products for the “High Velocity Hurricane Zone” and “Large and Small Missile Impact”, or the Texas Department of Insurance Windstorm Inspection Program for the Inland I and Seaward Zones and tested by an approved inspection agency to indicate compliance with the requirements of AAMA/NWWDA 101/I.S.2. The certification program label also includes a tab that references AAMA 506-2000 and that the product conforms to ASTM E 1886 and E 1996-02 with a missile level of D. All windows should be certified that they were tested to meet a Minimum Design Pressure of +/- 60 psf. All windows are to be labeled to certify that they meet all these requirements.

Mulling: All multi-panel window groups are to be structurally mulled in a waterproof manner in accordance with the requirements of either the Miami-Dade County Building Department Approved Products NOA or the Texas Department of Insurance Windstorm Inspection Program Certification Report at the full DP rating.

Hardware: All frames are to be white µPVC plastic, with fusion welded corners. All operational hardware, including screws and hinges, is to be stainless steel, preferably type 316.

Exterior Pane: PPG SunClean hydrophilic glass (http://www.suncleanglass.com/)

Impact Glass Interlayer: Sentry Glass Plus (SGP) preferred; Polyvinyl Butyral with PET interlayer (next choice); Polyvinyl Butyral (lowest choice).

Optical / Thermal Performance: All windows are to have the following characteristics:
Visible Light Trans: 66% or greater
Summer U (day): 0.16 or less
Winter U (night): 0.22 or less
Shading Coefficient: 0.49 or less
SHGC: 0.40 or less
Relative Heat Gain: 100 or less
UV Blockage 99% or greater

Additionally, “warm edge” insulating spacer technology (preferably non-metallic) is to be used in all applications. Krypton gas fill should be considered, if required, to meet thermal insulation characteristics.

Information to be provided:
1) Copies of certifications from either the Miami-Dade County Building Department Approved Products List or the Texas Department of Insurance Windstorm Inspection Program.
2) A cross-sectional view of the proposed window glass buildup, identifying materials and thicknesses of each layer.
3) Model estimate of all of the thermal and optical properties of the windows proposed.
4) Air infiltration rate at specified wind speed
5) DP rating for water intrusion
6) Water infiltration rate at specified wind speed
7)Copy of warranty for the windows proposed.
8) Rough opening required for each window or mulled window combination
9)Detailed installation instructions to meet certification requirements
10) Recommended flashing instructions

Then the question: Who can make these windows? Vince had spoken at length with a company in Canada who could meet our specs and were competitively priced. Sadly, the owner died and the company closed literally on the day we wanted to order windows. Vince came up with a list of about 18 window companies who met our criteria and asked me to read web-sites and to call each one to talk with an engineer about putting our windows together. That was an intriguing process. I spoke at length with some excellent folks and was completely brushed off by others. Some sales people told me that I really didn’t need everything in the specs, which wasn’t the question. In the end, the competitive group became Jeld-Wen, Shwinco, Megrame, and Kolbe, both because their windows met our needs and also because of their responsiveness.

Lined up in the house ready to be installed are the new Shwinco windows! Shwinco is a family business based in the hurricane alley states of Alabama and Florida. When I was given the name and number of an engineer to call, it was Jerome Shipp, the founding engineer, who answered my call. That’s not just ANY engineer! His son, Craig Shipp, Sr., is the company president, and there are several other family members who work there, including Craig Shipp, Jr. Jerome and Craig, Sr. took a lot of time to speak with us, even though we are private home owners and not a big corporation. They make an impressive window but were also willing to do some things slightly differently for this application. Craig, Sr. even looked at our house plans and offered some suggestions for a stronger window plan on the east stairwell wall, which we were happy to use. The finished product is an amazing window that is very strong, very energy efficient, very beautiful and incredibly heavy. (They weigh in at 15-20 pounds per square foot, and some of the windows are 6’ x 6½’.) When the windows were delivered, Craig, Sr. actually called to check on the shipment. The Shipps obviously care about their products. They have worked hard and worked together, and the teamwork clearly shows in both the windows and in the service they offer. The only thing they don’t have is a distributor on the Outer Banks, and that would be a great asset to our community.

There is a video on the Shwinco web-site called the Baseball Challenge. It is an entertaining and truly informative video showing what happens to windows in hurricanes. Watching this, while fun, shows exactly how a properly designed impact resistant window can determine whether a structure survives or fails in a big storm. It involves trying to break windows with bats. Guess who wins! Take a look:

http://www.shwinco.com/videos/baseball.htm

If you want to learn more about Shwinco windows and other products, their web-site is at:
http://shwinco.com

Vince and I want to offer many thanks and a round of applause to the Shipps for solving a big and very important structural component for the house that will bring the beauty of the beach into the house. Of all the things that will make our house home, the windows will be what lifts our hearts every single day, and that is quite an accomplishment!

There has been a lot of wind on the beach this week, so the windows are yet to be installed. Just getting them into the house was quite an undertaking with a 25 knot wind. It took some good old OBX ingenuity and a calm and patient soul manning a boom truck, but all 35 windows are safe and sound without a scratch. Here’s the video of that dramatic afternoon:

"She's blowin', she is!" a note about nor'easters

There is a lot of conversation about wind here on the Outer Banks. The strength and direction of the wind shapes the tide and the goings on for the day. A shift in the wind literally changes the life agenda on the beach, determining whether it is a good day to go fishing, which work gets done when, if the ocean is safe for swimming, or if it is a day to be spent tucked in at home. In any case, it is always a good idea to have a sweatshirt and a cap in the truck, because what feels like a comfortable breeze in Kitty Hawk could be a chilly wind out on the beach.

Jan DeBlieu, a long time Outer Banks resident who became the Cape Hatteras Coastkeeper in 2003, wrote a remarkable book about this force that keeps us always in touch with the weather. Wind: How the Flow of Air Has Shaped Life, Myth & the Land, is a wonderfully well-told story of both the art and the science of living with wind. Reading it, I am reminded of how nature’s elements often have many layers, each with its own set of influences over the way everyday life moves from morning into night.

When people hear that Vince and I are planning to live in North Swan Beach where there is no road and only the beach to use as a pathway, we are often asked what happens when the water is high and driving on the beach is impossible. The answer is simple, “We don’t go.” The truth is that with the right truck, it takes a lot not to be able to get back and forth if it is really important, but OBX common sense tells folks that risking the drive for ordinary things that will be the same tomorrow as today just isn’t worth it. If you want your vehicle to last, don’t drive it through salt water.

This season’s batch of early fall nor’easters has caused some delays for the house, with the first storm near the end of September blowing enough sand to cover the lumber piles on the job site, removing a lot of sand from under the house, and turning the road behind our house into a river. It seems that October has been one nor’easter after another, with many days of high surf advisories limiting the time the workers be up the beach and get safely back to the road. For us, it has been a bit frustrating and inconvenient, but we have had no actual damage. For the folks to the south in Rodanthe, the winds and the high water have brought situations that have been much more serious. A nor’easter is not something to be taken lightly, sometimes causing more damage than a hurricane largely because of the tenacity and duration of the storms. To live on the Outer Banks, the wind and whatever it brings must be accepted with patience and being prepared to hunker down for a few days at home.

Here is a little video that was posted on You Tube in September by neighbors just north of us, showing the surf coming all the way up to the dune line. Our dune wasn’t breached by this storm, but the tide definitely came up to its base.



There is a slideshow on the Local News Page on islandfreepress.org showing high water in Rodanthe. Take a look at what has happened from the nor'easter: http://tinyurl.com/58jabo
That is what we are hoping to avoid, though it could be any of us.

So now, a lot of tasks have been finished up: The cross braces and threaded rod tie-downs have been installed, the main roof is dried in, the window openings have been cut, and the Currituck County sheathing inspection has been passed. The next task is to get that west entry completed so that the windows can be delivered and installed!!!