Air Supply

When I was a young teenager in general science class, my teacher tried to explain that color exists only when there is light. At the time I had a pink bedroom that in my mind stayed the same color all the time, day or night. Since every time I peeked at it in the night with a flashlight, it WAS pink, then obviously just because I couldn’t see in the dark didn’t mean the room was not pink. Right? Wrong! Sigh. I still struggle with that concept, but now I do understand it. I don’t like it, but I accept it. Comprehending what Vince has planned for what could literally be called “air conditioning” has been a similar struggle. My experience with heating systems has been more in relationship to the location of the thermostat than in understanding exactly how the warm or cool air is produced, and my habit is to simply open a door or window when I am uncomfortable. See the problem?

There are three big goals for the Heating, Ventilation, and Air Conditioning (HVAC) systems in the house: Climate control, efficiency, and air quality. This sounds simple, but there are a lot of factors to be addressed in each category. Temperature control is quite manageable most of the time, since the Outer Banks enjoys an average annual temperature of about 63 degrees and a comfortable indoor temperature would be around 72 degrees. There are fewer than 10 winter days of with temperatures below freezing and only a few weeks of weather that is 90+ degrees in the late summer. Controlling humidity is more challenging, with a high average annual humidity at about 75% and the comfort level for humans in a house between 40% and 60%. We humans make a habit of increasing that level in the house just because we breathe, move around, cook, do laundry, play, have pets, sit by the fireplace, on and on. As for efficiency, our only choice for continual power is electricity (with a back-up generator), because there are no sources for fossil fuels or wood in our area of the beach. Protecting the equipment is important as well, because being on the oceanfront exposes anything outside to a lot of variables, like heat from the sun, changing winds, exposure to salt air and a huge body of water that occasionally comes for an uninvited visit. In general the Outer Banks has very clean outside air, but maintaining good indoor air quality is a different challenge. Often, people don’t think about what they are breathing, but with the lack of air infiltration in a tightly closed structure and the amount of Volatile Organic Compounds (VOCs) and other emissions that are a part of modern life, indoor pollution control is an essential idea. As with the siding, solving one issue impacts another, so that the whole house is really an integrated sum of its systems, rather than of separate parts…like a person, in a way. Given these constraints, Vince decided to use a closed loop geothermal heat pump system aided by a whole house dehumidifier. He added energy recovery ventilators (ERVs) to assure an efficient system for maintaining good indoor air quality.

Before this project, the only thing I knew about a heat pump was that it doesn’t produce its own heat. In a nutshell, a heat pump moves heat from one source to another, and that source can be the outside air, water, or the earth. An air-to-air heat pump system is the most common, but often the difference between the outside air and the desired household temperatures overwork the heat pump and cause it to be less effective and inefficient. In an air-to-air system, the work
that the heat pump must do is greatly variable depending on the vagaries of climate, which makes it difficult to correctly size the heat pump unit. Water-source heat pumps are much more efficient than air-source units and are often used in large commercial buildings, but they require a fossil fuel fired boiler system to produce heat in the winter. For our use, the geothermal heat pump makes the most sense, especially since the earth where we are maintains a constant
temperature of about 61 degrees Fahrenheit starting ten feet below the surface. Another benefit of a geothermal system is that the compressor and heat exchanger sit inside the house, where they will not corrode. Very important for a salty area. This article and illustration from the Consumer Energy Center has a very clear explanation of a closed loop system:

http://www.consumerenergycenter.org/home/heating_cooling/geothermal.html

Here's a video that illustrates how a heat pump works:



and another about the geothermal system:

Our choice for the HVAC sub-contractor was R.A.Hoy, one of the oldest HVAC contractors on the Outer Banks. (http://www.rahoy.com) In addition to being knowledgeable and experienced regarding the geothermal system, the guys are great to have around the work-site. They put in long days of continual work, but they are laughing and fun and happy to explain all they are doing in the moment. The installation supervisor for our job is Fred Marklin, with Toby and his apprentice, David, putting the ductwork together for the rough-in. It has been interesting to watch how something that looks like big Legos when it arrives in the truck comes out being neat and orderly installed. We had planned for the placement of the ductwork when we designed the house, but there still were challenges associated with feeding the hard ducting through the chase in the middle of the house and allowing space for insulating the roof deck on the top floor.

The ducting is rigid galvanized steel except for the last few feet of the branch runs, where the ducts are flexible aluminum. The rigid duct is harder to handle, but it prevents the trapping of dust in the system because it is smooth. To prevent air leakage and air infiltration, mastic was used where two pieces of duct come together, and in some places aluminum tape was used instead. The tightness of the duct lines also contributes to the indoor air quality, because the system remains uncompromised. In our house, all of the ductwork is internal to the house, so there is less opportunity for the growth of molds and mildew. Each duct is insulated with aluminum faced fiberglass batts.

The house will have two complete HVAC systems, one for the top floor and one for the bottom floor. Steve Jenkins, our mechanical engineer, determined the sizing of the heating and cooling systems using Air Conditioning Contractors of America (ACCA) Manual J-compliant software. Although the Manual J is a complicated calculation, it prevents the incorrect sizing of the system and lessens the possibility of an uncomfortable living environment and wasted energy. Steve also performed the Manual D calculations, which establish the correct sizing of the ducts. (These Manuals are actual books, which are alphabetically named technical instructions for many different HVAC calculations, both commercial and residential.) A temperature control system is generally sized to the maximum expected thermal load of the house, so that the system can handle the worst temperature conditions. Unfortunately, since the usual operation would not be running at peak capacity, the system can become sub-optimal in terms of function. Our response to this is to have a two-stage heat pump which can also operate as a smaller system that is a sub-section of the actual heat pump (about 50% capacity). In this case, the system runs longer but is better able to remove the humidity from the air. It is important to realize that an HVAC system in a temperate climate is cooling dominated. Vince decided to use the WaterFurnace Envision series geothermal heat pump (www.waterfurnace.com) based on his research and Hoy’s recommendation. Florida Heat Pump (http://www.fhp-mfg.com) and Carrier (www.Carrier.com) are also good choices.

Contrary to his Sicilian heritage, my husband has an avid dislike for humidity and decided to use a whole house dehumidifier. Steve Jenkins provided Vince with psychometric charts which graph the physical properties of moist air at a constant pressure so that he could properly size the dehumidifying units. The units of choice are made by Honeywell:

http://www.forwardthinking.honeywell.com/products/dehumidification/dehumidification_products.html

Basically, the dehumidifier is a small, self-contained HVAC system that takes moisture laden air from the return duct, removes the moisture from the air and then sends it back either to the return duct or to the supply duct. It functions like an air conditioning unit by compressing the working fluid which runs through the cooling coils. The moisture laden air flows over the cooling coils, and the humidity condenses on the coils and is drained off as water. Then, the newly cooled and dehumidified air is run over the heat exchanger from the compressor and rewarmed. As air is cooled, its moisture carrying capacity decreases, so the moisture can be extracted. Vince explains that the process is like that of thermal fog, when warm air flows over a cool body of water and can no longer hold the physical droplets of water. In the house, the humidity will be measured and adjusted by a humidistat, which mounts on a wall and looks like a thermostat but has a humidity sensing element.

To improve and maintain good indoor air quality, Energy Recovery Ventilators in two zones will be used to actively manage the intake of air from the outside and the exhausting of contaminants and humidity from the inside. An Energy Recovery Ventilator (ERV) is a type of air-to-air heat exchanger that not only can transfer sensible heat (temperature) but also latent heat (in water vapor). Since both temperature and moisture is transferred, ERVs can be considered total enthalpic devices. An ERV takes the heat from the current air and transfers it to the incoming air stream, moving heat between the two air streams whichever way it needs to go. These mechanical ventilation systems use fans to maintain a low-velocity flow of fresh outdoor air into the house (incoming air stream) while exhausting out an equal amount of stale indoor air (exhaust air stream). Fresh air is supplied to all levels of the house while stale air is removed from areas with high levels of pollutants and moisture. Models with heat recovery and moisture recovery transfer heat and moisture from the exhaust airstream to the incoming air stream during the heating season, and transfer heat and water vapor from the incoming air stream to the exhaust air stream during the air conditioning season. An ERV runs on a proportional timer that is set up and monitored by the person (in this case Vince) who determines the appropriate need for air quality control.

Here's a great video explaining how ERV's work:

In the next couple of weeks, the ERVs will be roughed in by Hoy, and the dehumidifiers will be added after the heat pumps are installed. The ground loops, obviously integral to the system, are schedule to be installed by Steve Van Horn at Chesapeake Wells later this month. We're getting there!

Not by the Hair of MY Chinny Chin Chin!

The third little pig met a man with a load of bricks, and said, "Please, man, give me those bricks to build a house with." So the man gave him the bricks, and he built his house with them.
The wolf came, as he did to the other little pigs, and said, "Little pig, little pig, let me come in."
"No, not by the hair of my chinny chin chin."
"Then I'll huff, and I'll puff, and I'll blow your house in."
Well, he huffed, and he puffed, and he huffed and he puffed, and he puffed and huffed; but he could not get the house down.

The story of The Three Little Pigs is an English folk tale first written in the 18th century, but it is thought that the story and the lessons are much older. In the category of “Lessons Learned,” realizing that stronger materials make a stronger house is an important one to have on the list. On the Outer Banks, the material used to keep the house from being huffed and puffed away is not brick but fiber-cement board, and it is not only the quality of the siding but also the quality of the installation that keeps the wind outside. Our house is being beautifully “dressed up” by Lewis Babb, who owns a company called Exterior Specialists.

Before the siding is attached, the house must be wrapped and “weathered in”. The product choices for both the house wrap and the siding came by working through a series of causes and effects as each decision’s consequences affected the next. One early decision with impact on the siding processes was the choice of a dense closed-cell polyurethane foam insulation that is sprayed on the exterior walls inside the house. The foam expands, filling any open spaces to provide a continuous, protective air barrier that eliminates air leakage, a primary cause of energy waste. It forms a virtually airtight thermal, sound, and condensation barrier. Since the exterior walls are eight inches thick, there will be 2 ½ inches of spray foam with the remaining space being filled with fiberglass batts. It would be cost prohibitive (and not very smart) to fill the cavity with foam with no appreciable gain in the quality of insulation. Using the polyurethane foam prevents water and water vapor from getting through the sheathing into the house, which means that any water absorbed by the sheathing would be essentially trapped. Wet sheathing = rot and mildew = an unwelcome and far reaching problem. The question became how to either assure that the sheathing could dry when it became wet or to prevent the sheathing from ever getting wet. After looking at the more traditional house wraps, like Tyvek and tar paper, Vince decided to use an impermeable application and chose Grace Perma-Barrier wall wrap to keep the sheathing dry. This Grace product is a self-adhesive, rubberized, asphalt/polyethylene waterproofing membrane that is applied directly to the sheathing. Correct installation includes a specific amount of overlap and “rubbing” the material to provide secure adhesion, and the butyl rubber adhesive literally melts into the house. With this product on the outside and the foam on the inside, the exterior sheathing is sandwiched between two impermeable substances. That sounds ideal, except that there must be a way to assure good air quality and for moist air that accumulates inside the house (people breathing, doors opening, washing machines, etc.) to get out. The answer to this problem is an ERV (Energy Recovery Ventilator) that is a part of the whole-house HVAC system. The ERV recaptures heat from the air stream and replaces it with fresh, cooler air through the use of an air-to-air heat exchanger. (More on that later!) Applying the Perma-Barrier was problematic because it was something different to the crew, and it required a lot of time and patience to put it on smoothly and to go back and literally rub the entire house for good adhesion. That’s a lot more work than just nailing up tar paper! Grace makes another house wrap product that literally sprays on like paint, but that would have been even harder to apply correctly in our windy environment.

Years ago, when beach houses were not used in the winter, the issues of mold and rot were almost non-existent. Since there was little or no insulation in a house, anything that got wet would be open to the air and simply dry out. Over the last fifty or so years there have been a lot of changes in how houses everywhere have been made more comfortable. At first there was just sheathing and siding (primarily wood or brick), and then there was sheathing and tar paper and siding, and now there is sheathing, house wrap or tar paper, siding, and insulation in the interior part of the house envelope. Insulation solved the problem of keeping the interior of the house more protected from the weather, but it caused the secondary issue of not allowing the sheathing to dry by reducing the air flow through the wall. Moisture and reduced air flow causes mold and rotting, and that’s the “circle” of dominos to work through.

One solution came in the 1960’s, when the National Building Council of Canada began to address problems associated with the deterioration of sheathing and siding. It had been noted that the air inside various structures was becoming increasingly humid, which indicated high water absorption. It was determined that the increasing water absorption was caused by advancing deterioration of the sheathing, which was then transferred into the house. A process was developed to create a physical separation between the siding and the sheathing, called a pressure-equalized rain screen wall. The concept is to deflect water absorption into the sheathing by tackling the forces that drive water into the building shell. By neutralizing these forces, rain screens can withstand extreme environments. The rain screen wall is created by the use of vented or porous exterior cladding, an air cavity of a few inches, and a drainage layer on a rigid, water-resistance and airtight support wall. Rain screens effectively "drain the rain" by controlling powerful building wetting forces-gravity, capillary action, and wind pressure differences.

Here’s how it works: The exterior cladding deters surface raindrop momentum. It is typically porous with several air bypasses. An airspace separates the cladding from the support wall. The airspace decouples most of the cladding from the support wall, thereby reducing splash and capillary moisture transfer. Protected openings (e.g., vents, or weep holes) positioned at the top and bottom of the wall promote convective airflow, allowing moisture to quickly drain or evaporate from the air cavity. The exterior face of the support wall is protected with a drainage layer to further protect against any moisture that bypasses both cladding and air cavity. The wall air tightness (i.e., sealed assembly) buffers the remaining differential air pressure force. A “pressure-equalized” rain screen wall means that the pressure between the siding and the sheathing becomes equal to the outside pressure. The velocity component of the wind has been removed, preventing the wind from forcing water into the house. Since the siding and the sheathing are no longer in intimate contact with each other, the siding essentially absorbs the momentum of the wind. (That’s why face-nailing the siding with stainless-steel ring shank nails is so important!) Water that penetrates the siding freely drains down the membrane-wrapped sheathing, and any water that doesn’t drain evaporates. Cor-a-vent siding vents have been added to help promote air movement along the rain wall and to prevent various critters from colonizing behind the siding. Additionally, stainless steel drip edges were installed along the bottom of the siding to take the draining water away from the house and prevent the soaking of the foundation.

Our siding of choice is Hardi-plank. Fiber-cement board was chosen because it meets the requirements of a tough coastal area, and Hardi-Plank was chosen because it has a resume that backs up its qualifications. It has passed Miami-Dade testing for wind gusts of 150 mph and is rated to withstand both large small missile impact with tested design pressures of +53 and -53 (pushing and pulling). Hardi-plank also has FEMA approval for use in flood prone areas and is fire resistant. Those qualities provide a lot of assurance from James Hardie Corporation, but a key piece is making sure that the siding is installed according to the specifications for hurricane zones. That requires a siding installation crew that is patient and attentive to detail. We also specified that type 316 stainless steel fasteners be used, because no siding can do its job if the fasteners fail. Hardi-plank also comes pre-painted using a process called Color-Plus Technology. This application is particularly good for use oceanfront, because the paint is applied in a controlled environment before the siding is exposed to moist salt air or sand, and it has a 15 year warranty. In a cost comparison, the pre-painted product adds a small percentage of cost over the unpainted siding and is a big savings over having the house painted after installation. Louis has also made sure that the end cuts are painted before the boards are put on the house to prevent moisture from wicking through those vulnerable spots. Since the recommendation for hurricane zones is that the siding be face nailed, that also means that the nail heads have to be painted individually… one of the less desirable aspects of pre-painted siding. For this house, the trade-off was appropriate, and the siding will always have that first controlled paint application to protect it.

At the moment, Lewis and crew are close to finishing up their piece of the job, and each step brings us a little closer to seeing the exterior or the house as we planned it. Years ago, when we were up at the lot planting grass, I would take Vince’s arm and say, “Let’s pretend that we really do have a house here and that we have had a wonderful walk on the beach together. We would take the steps up from the beach onto our walkover and head into the kitchen for a cup of coffee or sit on the deck with a glass of wine.” And now, that vision is almost a reality!

I Can See Clearly Now: Installing the windows

I only drink fortified wines during bad weather. Snowstorm, hurricane, tornado--I'm not particular, as long as it's bad. After all, any storm for a Port.
Paul S. Winalski

Even with a very strong window, there are two remaining concerns: 1) The strongest window in the world will not save a house in a storm if it doesn’t stay in its opening, so the way the windows are installed and sealed makes a big difference in the security of the structure. 2) Water penetration around the window from horizontal, wind-blown rain can wreak havoc in the forms of rot and mold in both the interior of the house and within the walls. Windows are designed for both positive and negative design pressures (DP). Positive pressures are those acting to push the windows in from the outside, and negative pressures are suction forces trying to pull the windows out of the house. Both types of forces need to be addressed to withstand a hurricane. Shwinco windows use a type of tie bracket that is screwed around the edge of the window and spaced to withstand a given load. These clips are screwed into the framing and prevent the windows from popping out. There is also a nailing flange that is made from a very stiff vinyl. A strong polyurethane adhesive is applied around the flange, and then the flange is nailed as the window is set. The flange faces the outside of the window opening and keeps the window from being pushed into the house. It is important that the rough openings for the windows be kept tight for this purpose. The window literally uses the house to push against as its support, so the integrity of the framing helps to maintain the integrity of the window system. The need to maintain structural strength reinforces the need for fasteners that don’t corrode, like type 316 stainless steel, so that any pieces that do get wet or damp do not weaken with time.

Different environments cause varying potential loads, which drive the decision for applicable design pressures and allowable window sizes. Since the windows are edge supported, the building envelope must be able to support given loads, determining the maximum sized windows that will still meet the positive and negative design pressures in a situation. A fixed window can be larger than an opening window and still uphold the needed DP, because the glass in a fixed window is incorporated into the window frame, which stiffens the frame and makes it stronger.

Preventing leaks in a high velocity hurricane zone is an entirely different beast to conquer. Prior to installation, the window opening is prepared and sealed. For this application, Dupont Flex Wrap was applied snugly around the rough window opening and OVER the house wrap to maintain a waterfall concept for possible water flow. (FlexWrap is a flexible, self-adhesive flashing tape constructed from a layer of tough Tyvek laminated on a layer of high adhesive butyl rubber.) Because it bends, this product goes around corners without having to be cut and fitted, lessening the chance for a leak in an awkward spot. To get a snug application, the FlexWrap should be “rubbed” into place for good adhesion to the surface. This flexible tape is tested for water intrusion both as a newly installed item and also after thermal aging.

Once the window is in place, a drip edge is installed across the top of the window. A drip edge takes the water off the plane, so that accumulated water falls beyond and not down across the window. The bottom of the window is not sealed and not nailed. Shwinco windows have a weep mechanism that allows water to drain out if it gets past the first seal, and the windows actually have three seals to keep water out of the house where the window meets the frame. If the window is designed properly and the path is not blocked, gravity will take any water out. The rough opening under each window has an added piece of sloping cedar under the FlexWrap as an added assurance that the water will run in the right direction and not pool in the window sill.

Here is a slideshow of some of the first floor windows being prepared and installed:

A note about casement windows versus single hung windows: Single hung windows are intrinsically more prone to higher leakage rates simply because the opening part of the window has to slide in a channel and needs clearance (space between the window and the frame) to do so. A casement window, in contrast, is closed up against the window opening and is locked down, eliminating virtually all clearance when latched.

When designing a house to a certain type of constraint, like withstanding a hurricane with 150 mph winds, it is important to realize that being willing and able to compromise in terms of design can mean the difference between saving and losing a house. In the end, the questions to ask oneself are those that begin with “what if,” or “when” a storm comes. We happen to really like casement windows, but even if we didn’t, it would be easier to accept the casement windows than it would be to face the loss or damage to the house.

With the window specifications that Vince ordered and Shwinco manufactured, and with the careful installation by PJ Stuart and Currituck Construction Company, we have given the house a good fighting chance in a big storm, though it will be perfectly OK not to ever test the house and the windows to their full capacity.

For what I have received, may the Lord make me truly thankful.
And more truly for what I have not received.
Storm Jameson

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!!!

Raising the Roof

Compromise makes a good umbrella, but a poor roof.
James Russell Lowell (1819-1891)

All creatures take shelter from the storm. One of the feral cats who lives behind our house created a nest in the base of a bush near the back yard. Toads burrow snuggly into piles of sand near the walls of the house, and foxes make dens in hollow logs or trees. It is thought that more than 35,000 years ago, Neanderthal man created structural frames from mammoth bones and covered them with animal skins. Since that time, humans have made roofs using everything from “ready made” caves to sod over birch bark, sapling webbing covered with animal hides, and the ever popular thatching. Fired roof tiles were found in Greece as early as the 3rd millennium BC! Over the many years that people have been covering both heads and belongings with something installed over their dwelling places, man has learned to some degree which materials work better than others and also developed new ways to stay safe and dry. I remember hearing as a child, “As long as the roof doesn’t fall in, we’ll be OK,” in response to anything potentially dire. Simply put, it is common knowledge that a roof to call one’s own is both necessary and important.

The decisions about the roof for the new house were made before any other ideas were put in place. The plans for the strength and security of the roof made all other design decisions secondary, much to the frustration of the architects. To decide on the shape and pitch of the roof, Vince read all of the existing FEMA reports and gathered information from other sources like the International Building Code, the Coastal Construction Manual, Miami-Dade and the Texas Department of Insurance. From these sources, he learned that the roof pitch had to be between 4/12 and 6/12 to withstand the wind loading from a big storm. (A roof’s pitch is the measured vertical rise divided by the measured horizontal span, like slope in geometry.) A roof with the wrong shape and slope can literally become a giant wing in heavy winds, lifting itself off the house. If you lose the roof, you lose the house, so this piece of the design was critical. Our roof pitch is 5/12. It is acceptable to have a slightly different ratio, but it is more important to have the roof stay on the house than to have an extra foot of interior width. We had to be careful not to let this number slip too far from the appropriate range when planning the living spaces.

Roofs can be made in many different variations of angles and planes. This house will have a “hip” roof, which means that all sides slope downwards to the walls, usually with a fairly gentle slope. It is a house with no gables or other vertical sides. Since a hip roof is self-bracing, it does not need the same amount of diagonal bracing (wind bracing) that a gable roof requires. Our house is rectangular, so it will have two triangular sides and two that are trapezoidal. On a rectangular plan, a hip roof has four faces that are almost always at the same pitch or slope, which makes them symmetrical about the centerlines. (On a square house, a hip roof is shaped like a pyramid.)

Because they require a more complex system of trusses, hip roofs are somewhat more difficult to construct than a gabled roof. Although the roof itself is harder to construct, the walls that carry the roof are easier to build, being all one level. The triangular faces of the roof are called the hip ends and are bounded by the hips themselves. The hips (where the planes meet) sit on an external corner of the building and rise to the ridge.

One downside to a hip roof is the lack of space within the roof structure to use for other things. There was a recent change in the height allowance by Currituck County, allowing the 35’ maximum height to be measured at mid-roof rather than at the peak of the roof, and that extra footage allowed the ceiling heights to be at 9' with the roof pitch staying where it should be. Once the two main roof decisions (roof shape and roof pitch) were in place, the constraints established by them were concrete. End of discussion. This is why, as mentioned in the earlier, we will have a house that is a beautiful shoebox.

Here is the section of Vince’s specifications for the roof framing:

8) Ceiling and Collar Joists – Roof trusses provided by Universal Forest Products designed for 150 mph wind loads. End sections (extending beyond the walls) are to be pressure-treaded wood (Forest Products ProWood® Micro).

9) Rafters - Trusses will be anchored to the walls with type 316 stainless steel nailing brackets per engineered plans if there is potential for exposure to exterior moisture. Brackets that are completely internal to the envelope and insulation will be hot-dipped galvanized steel.

10) Sub Fascia - 2" x 6"

11) Hips, Valleys, and Ridges – Roof Trusses provided by Universal Forest Products.

12) Roof Sheathing - 5 ply, ¾” CDX pressure-treated (rated for ground contact), exterior-grade APA Structural I rated plywood, glued and screwed using 2 ½” long type 316 stainless steel screws. The first course of plywood is to be ¾” 5 ply, CDX pressure-treated, exterior-grade APA Structural I rated plywood, glued and screwed using 2 ½” long type 316 stainless steel screws, and completely covered by a “peel & stick” rubber membrane sheet (at least 60 mils thick). Provide adhesive fillets on interior of all roof sheathing.

Vince chose to use engineered and manufactured trusses to be assured that the roof could carry the wind loads. A stick built roof system doesn’t have the same series of checks and balances as those planned by a structural engineer. Johnny Ghee, who also designed the interior trusses, engineered the roof trusses. Johnny has to his credit a unique design feature for roof trusses, based on requests that he was frequently getting for a more authentic 1940’s beach cottage look. In the design of the truss tails, which should be treated for his application because they are exposed, the tail is offset ¾” lower than the actual truss. This leaves enough space for there to be an additional piece of plywood (usually a simulated bead board) to be placed so that the house has a more traditional look. To accomplish that look without Johnny’s innovation, the trusses would have to be stick built, and the roof would not be as strong. It’s a great idea and a way to add an interesting architectural feature within a structurally sound roof. Our house is more contemporary, so we aren’t using that look, but we wanted the treated tails anyway.

Because there are screened porches on either end of the house that are under roof, Vince designed the porch roofs as separate entities, so that the main house roof would not be damaged if the porches broke away during a storm. This means that the main roof will be built and sealed before the porch roofs are added. The trusses for the porches were to be designed as separate from the house. Unfortunately, the trusses and porch roof for the north side of the house were mistakenly designed as being integrated into the main house roof, so we now have had considerable delay while we wait for the new trusses and for the double galvanized truss plates that hold them together. This was much too important a part of the structural strength to let pass: “If you lose the roof, you lose the house.” So far, the two biggest mistakes have been because the trusses were manufactured incorrectly. It’s unfortunate, because even though Universal Forest Products replaces them correctly or helps with the field repairs, it costs us time and effort. Luckily, the mistakes have been caught while they can be fixed, but it definitely isn’t a good thing, and it’s hard to understand why it has happened. The new trusses will be delivered and installed next week (10/7), and then we can finally get the house under roof. Much to his credit, Vince did not “go through the roof” over this error. I could not resist adding that!

When riding along the roads of the Outer Banks, you see that most houses have little square vents all along the sides of the roof. There are also chimneys and skylights and exhaust pipes for one thing or another. Vince has been adamant all along that there be no penetrations in this roof, because wind blown rain can get into even the smallest space and cause a leak. In the end, there may be something that must be vented through the roof, but hopefully that can be avoided. The roof specifications call for 4” of closed cell polyurethane foam (2.2 lb per cubic foot) that is applied directly to the roof deck and covered with 12” of unfaced fiberglass batts, which as a side benefit leaves no room for there to be heat building up between the insulated space and the actual roof. This translates into a nice feature: No need for roof venting!

Once the framing is completed, the roof is tied to the house with tie-downs made of galvanized steel. The tie-downs have an important function, because they carry the load path from the roof of the house all the way to the pilings. When the wind exerts a lift force on the roof, it will in effect be pulling on those very deep pilings. The tie-downs that Vince has chosen are larger and stronger than needed, because…If you lose the roof, you lose the house!

May you always have walls for the winds, a roof for the rain, tea beside the fire, laughter to cheer you, those you love near you and all your heart might desire

Irish Blessing

Oh, wow! Second floor framing

Although there is still only a ladder to climb from the ground to the first floor, there are now steps inside that go up to the second floor. I have seen those steps many times in my mind's eye, but it was wonderful to walk up with the sea in full view and finally see our ideas coming to life. The second floor will be where we spend most of our time, with the kitchen, open living area and bedroom suite up there. In comparison to many things, our house isn't really high, but it feels like an aerie with the whole world in view. The thing that I found most wonderful was that my husband, whose incredible mind and talented eye for detail and space, had really taken all the things that we thought about for our home and made them real. I knew what I wanted to see and feel within the house, but Vince has the ability to translate an idea into inches and feet and places to sit and windows that go on forever. When he was able to go up to stand in that space, I walked with him over to where the kitchen will be and said, "What do you think?" He said, "This is what I wanted all along...to be able to prepare a wonderful meal and to be able to see." That makes it worth whatever it takes.

So much of what we have to say about this house relates to the specifiations and structural pieces that make the house strong. The heart of the house comes from our ideas about how we want our time together to be, and that's what makes it beautiful.