Winter Panel Homes StructureWall Q & A #S-3.1

GENERAL

What are the advantages of panelized construction over conventionally framed buildings?
Panelized homes, made with Structurewall™ stresskin panels, can be erected very quickly. They provide tremendous interior design flexibility. They also produce a stronger wall than conventional framing of equal thickness, and they are extremely energy efficient.

What holds the house up since standard framing lumber is not used?
Structural support is provided by the panel skins. Structural stresskin panels use more wood than conventional framing, but it is optimally placed (as the panel skins), resulting in a wall assembly more than twice as strong as a conventional 2x4 wall. The 4-foot-wide panels, up to 28 feet long, are securely held together with plywood "splines" in both wall and roof systems.

What are the disadvantages to this type of panelized construction?
Stresskin panel construction is still quite new; many builders are not familiar with erection of the shell and techniques used for finishing. Fortunately, shell erection is handled by an experienced crew provided by Winter Panel Homes, or a qualified local contractor. Techniques required for construction are very easy to master, and are covered in the Construction Manual for Winter Panel Homes.

Is there an advantage to the 4½" panel thickness?
Yes. This construction system provides the highest level of energy efficiency for the given wall or roof system available anywhere. You get more living space than in any other comparatively insulated house with the same outside dimensions. Also, windows and doors can easily be installed with little or no modification of the jamb thickness.

What is the interior layout like in a Winter Panel Home?
Because the building shell provides most of the load-carrying strength of the house, there is tremendous flexibility of interior design. Use a Winter Panel Homes design, plan the layout yourself, or work with your architect, builder, or Winter Panel Homes representative to provide exactly what you need. Unlike with most houses, the structure itself does not constrain your design flexibility.

STRESSKIN PANELS

What are stresskin panels?
Stresskin panels are insulated building panels which have a core of rigid insulation between an exterior and interior skin. The Structurewall panels used in Winter Panel Homes are manufactured by Winter Panel Corporation, and have a 3-5/8" core of polyisocyanurate foam insulation, with waferboard or oriented strand board (OSB) skins on both the interior and exterior. The two skins carry all the loading stresses of the structure, while the foam core keeps the two skins aligned.

What skins are used on the panels?
Structurewall panels have an exterior grade of structural waferboard or OSB on both the exterior and interior.

How are panels made?
Panels are made in a continuous lamination process in which the foam is injected between the two waferboard skins and allowed to expand and bond to the waferboard under carefully controlled conditions.

Why is waferboard used instead of plywood?
For a number of reasons. First, waferboard is more stable than plywood, particularly in high moisture conditions; delamination and linear expansion are much less likely to occur. Second, waferboard is available in much longer lengths (up to 28'). Third, it is less expensive than plywood, producing a more affordable finished product.

Are there any problems with dimensional stability of panels?
Panels are quite stable, but will expand somewhat under high moisture and temperature conditions. At 160°F and 100% relative humidity, panels will expand 5% over 24 hours. Lowering the temperature to -20°F will result in a .15% volume decrease over 24 hours.

What is the R-value of the panel?
The minimum R-value of Structurewall panels is 26.5. The total system R-value is approximately R-28 (this includes the R-value of the panel, drywall, air films, and siding or roofing).

Are these "aged" R-values?
Yes, they are conservative values, aged a minimum of twelve months.

Why isn't there a vapor barrier in the panel?
The panel itself serves as the vapor barrier. Most model building codes require a vapor barrier with a perm rating of 1 or less. The perm rating of our panels is less than 1. Because there are no voids in the panel where moisture could condense, moisture problems are not a concern. Panels will absorb and release some moisture on a seasonal basis, just as the wood in a log cabin does, but there are no harmful effects of this cycling.

Do I need to add a vapor barrier or use a vapor-retardant paint?
No vapor barrier is required with the panel. The only place where moisture migration could conceivably be a concern is at panel joints. Joints between panels are sealed during installation to prevent moisture migration.

Do I need to allow an air space for ventilation on the roof if I'm using panels?
In most cases, no. Ventilation is usually only required on roof systems where moisture could condense in the roof system, or where high temperatures could damage the insulation. Neither of these is a concern with our panels. While some concern has been raised over the installation of asphalt shingles directly over a stresskin panel deck, at least one major manufacturer (Elk Corporation) has specifically approved the use of their shingles directly over Winter Panel Home roof decks, without loss of warranty coverage.

With a rigid shingle roof, such as wood shakes, tile or slate, horizontal strapping is generally recommended (follow roofing manufacturer's recommendations).

Do Winter Panel Home shells carry a warranty?
Yes, Winter Panel Homes carry a ten-year limited warranty covering the structural panel house, provided the house is erected in accordance with company guidelines. For complete warranty information, contact the company.

ENVIRONMENTAL AND HEALTH CONCERNS

What kind of foam is used in the panel?
Polyisocyanurate, an advanced formulation of urethane, developed for high R-value, structural strength and fire safety.

Is there any outgassing from the foam? What kind of gas is it, and do I need to worry about it?
Freon is used as the blowing agent for the foam. A very small amount of Freon will outgas from the foam over time, but the gas is considered completely harmless. It has been used as a refrigerant for many years, with no detrimental health effects.

Is there any formaldehyde in the foam?
No.

What about formaldehyde outgassing from the waferboard?
Exterior grade waferboard, such as that used in Structurewall panels, is made with phenol-based resins that do not release significant amounts of formaldehyde gas. Urea formaldehyde resins, on the other hand, which are used in interior grade particle board products, release far more formaldehyde gas, and it is these products — not waferboard — that have heightened concerns over formaldehyde in houses. The Federal Government requires that warnings be put on products that may release formaldehyde; our products do not require that warning.

What happens when the panels burn?
When the panels burn, a number of gasses are given off. Some of these are dangerous, including carbon monoxide and certain hydrocarbons. The exact composition of combustion products depends on the fire conditions (how much oxygen is available, etc.). You should assume that the gasses given off by all stresskin panels are dangerous. The toxicity of gasses given off from our panels during combustion is about the same as that from white oak or Douglas fir.
A key advantage of urethane foam is that the foam does not melt. Urethane is a "thermo-set" plastic and will retain its structural integrity until consumed by fire (like wood). Other types of foam melt with temperatures as low as 170慚, and can contribute tremendous quantities of fuel to a fire very rapidly. Additional information on fire safety of panels is available from Winter Panel Homes.

What is the wall finish fire rating of Structurewall™ panels?
ASTM testing by an independent laboratory showed the wall finish rating of Structurewall panels to be greater than 15 minutes with drywall attached. Complete information on wall and roof finish ratings is available from Winter Panel Homes.

What are the building code requirements for panels relative to fire?
Building and fire codes vary from place to place. Usually, a 15-minute finish rating is required for light construction. Structurewall panels, with an interior layer of ½" drywall, exceed this requirement substantially.

Do I need an air-to-air heat exchanger?
Air-to-air heat exchangers, and/or other types of mechanical ventilation, are recommended in all tight houses, including those enclosed by stresskin panels. Winter Panel Homes recommends that air-to-air heat exchangers be incorporated into all stresskin-clad houses.

ERECTION OF THE SHELL

Who takes care of erecting a Winter Panel Homes shell?
Either Winter Panel Homes, Inc. or its local independent representative is responsible for shell erection, with the work performed by a fully trained local rep or subcontractor working for Winter Panel Homes.

What are the foundation requirements?
The buyer is responsible for having the foundation installed to the specifications provided by Winter Panel Homes. An Winter Panel Home can be built on a slab-on-grade foundation, or on frost walls over a full basement or crawl space. It is extremely important, however, that the foundation is built to close tolerances. Because of the accuracy of the supplied components, even slight inaccuracies in foundation level and squareness can result in problems with shell erection.

How long does it take to erect a Winter Panel Home shell?
The complete shell, including walls, sub-floors and roof, can usually be erected in one week by a skilled crew. With large houses, or more involved custom designs, erection will take longer.

What happens if it rains while the shell is being erected?
Structurewall panels are not damaged by rain. However, long-term exposure to water will cause the waferboard at the panel edges to swell. After erection of the shell, these swollen edges should be sanded down with a belt or disk sander.

How far along will the shell be when the Winter Panel Homes crew leaves the site?
The shell will be fully erected and ready for window and door installation, roofing, siding and interior finish.

FINISHING A WINTER PANEL HOME

What skills are required for finishing a Winter Panel Home?
General carpentry skills are all that you will need to finish a Winter Panel Home. Skilled homeowners can do most of the work themselves, subcontracting out work requiring specialized skills, such as electrical and plumbing work.

How is the roof finished?
With asphalt and fiberglass shingles, panel joints are first sealed with asphalt roofing cement, then shingles are installed on the panels with an underlayment of roofing felt. Roofing felt is required. With some types of roofing, such as wood shakes and slate shingles, horizontal strapping is required. Follow manufacturer's instructions for installing shingles. Standard galvanized roofing nails hold very well in the waferboard.

What kind of roof trim can I use with a Winter Panel Home?
The outer roof edge, both along eaves and gable ends, will have two-by splines installed. You can add any trim to this you wish, to meet your design preferences. At the eaves, some people choose full-return horizontal soffits with ornate fascia trim, while others choose simple sloped soffits, nailed directly to the panel overhang.

Is exterior siding applied directly to the panel skin?
Usually. Felt paper and other moisture barriers should not be used between the panels and siding. An air barrier such as Tyvek™ or Typar™ may be used, but it is not required. In some situations, such as with wide board-and-batten siding, wood strapping should be attached to the wall first, then the siding secured to the strapping.

How should siding be applied?
Horizontal siding is nailed directly to the panel wall. Keep nails at least 6" from splines to avoid rippling of the siding. With shingles, you may nail into splines without worry. With vertical board-and-batten siding, horizontal strapping is recommended. Use 6d galvanized nails for clapboards and 8d galvanized nails for board-and-batten.

Are windows and doors difficult to install?
No. Windows and doors are very easy to install in a Winter Panel Home. Units are set into the rough openings (which were built into the shell) and shimmed to level, as per instructions provided by the window and door manufacturers. Then the perimeters are sealed with low-expanding foam sealant, resulting in an extremely energy-efficient installation. Care must be used when foaming around windows and doors so as not to swell the casings.

How are interior walls installed?
Interior partition walls are generally constructed of 2x4s and sheathed with drywall, as in conventional frame construction. Where an interior partition wall meets an exterior wall, the edge stud is nailed or screwed into the waferboard skin of the panel.

How do you run wiring in panels?
There are a number of options for running electrical wiring in a Winter Panel Home. Horizontal wiring runs are usually carried in the basement, with short upward extensions for outlets made in the Structurewall panels. Some electricians push the wire through the foam core of the panel, while others make a vertical rout through the inner waferboard skin from the outlet down to the floor level and push the wire in before drywall is installed. Other options include surface-mounted wiring and wiring concealed in a baseboard raceway. Winter Panel Homes has available a technical sheet on wiring details.

How are electrical boxes attached to panels?
The boxes are cut into the wall and either nailed to splines or secured to the waferboard with "Madison" straps.

How do you run plumbing in a Winter Panel Home?
There will be almost no differences between plumbing a Winter Panel Home and plumbing a conventional frame house. Plumbing runs should be kept in interior (conventionally framed) partition walls or in specially constructed plumbing chases.

How are walls finished in a Winter Panel Home?
Walls are usually finished with drywall on the interior face. On the stresskin walls, drywall is installed directly over the waferboard surface of panels, applied either vertically or horizontally. Some builders use construction adhesive in applying drywall to the panels, enabling them to use fewer fasteners. On interior partition walls (which are framed conventionally), drywalling is done in a standard manner, nailing or screwing drywall to the studs. With cathedral ceilings, some builders prefer to substitute Woodclad panels, which have an interior facing of pine, cedar, oak or cherry. The wood facing provides the required fire rating and offers the beauty of a natural wood. For information on Woodclad panels, contact the company.

How are kitchen cabinets installed?
Kitchen cabinets are very easy to install in Winter Panel Homes. Along exterior walls, cabinets are screwed directly into the waferboard skin of the panels. Because a single layer of waferboard is not as thick as a stud, you should use more fasteners. Screws are recommended for cabinet attachment. For the strongest attachment, cabinets should be secured directly to the waferboard, before drywall is installed, but it is possible to mount the cabinets to walls after drywall has been installed. On interior (non-stresskin) walls, cabinets are installed conventionally, by screwing or bolting them into studs.

What is the best type of heating system for a Winter Panel Home?
Any type of heating system can be used. Talk to your heating contractor or general contractor for recommendations.

Can I heat with wood?
Absolutely. Many people living in Winter Panel Homes are able to provide all their heat with just one to two cords of firewood per year! With wood heat, a source of outside combustion air is recommended.

Do I need to worry about insects with a Winter Panel Home?
On occasion, carpenter ants will take up residence in the Structurewall panels of a Winter Panel Home. To protect your house from possible ant infestations, Winter Panel Homes, Inc. recommends that you have your house protected by a certified pest control professional both during construction and periodically thereafter.

FOR MORE INFORMATION
For additional information on Winter Panel Homes prepackaged or custom house designs, and details on shell erection and finishing, visit our form or contact the company.

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