Stresskin panels have had a tremendous impact on the growth of timber framing over the past ten years. Panels allow you to quickly close in a timber-frame structure, providing high insulation levels while keeping your craftsmanship fully in view. To ensure highest satisfaction with stresskin panel installations, however, there are a few important guidelines that must be followed, both during panel installation and afterward.
This information sheet addresses several common points of concern in homes enclosed with stresskin panels. Most problems are easily avoided by following procedures outlined here and in the Timber Framer's Guide to Stresskin Panel Installation, published by Winter Panel. These guidelines are directed primarily toward the builder who is installing or overseeing the installation of panels. Some ongoing measures covered here are directed toward the homeowner. Upon completion of the project, you should pass along to the homeowners information on upkeep and maintenance, especially as it relates to moisture and carpenter ants.

Proper Storage and Handling of Panels
Keep panels as dry as possible, both before and during installation. Panels arrive at your building site wrapped in a protective "shed-pack" covering, which sheds rain yet allows panels to breathe. The shed-pack protects panels during shipment, but may not afford full protection at the building site. Once panels arrive, it is your responsibility to make sure they are protected from moisture and other damage.
At your building site, store panels off the ground on level blocking until use. If they are not going to be used right away, they should be stored under cover in a barn or shed. Make sure panels are stacked perfectly flat to prevent possible twisting. The blocking under panels should be on level ground or a floor and spaced no more than 4? apart.
Avoid excessive exposure of panels to rain. If possible, plan mound local weather forecasts and install panels when a several-day stretch of dry weather is expected. Curtainwall panels will withstand several wetting and drying cycles, providing they do not stay wet and are not moved while they are wet. If panels are allowed to remain wet, swelling of drywall surfaces and waferboard edges may occur, and drywall may mildew. If panels are move while wet, the paper on the drywall may peel off. Woodclad™; panels should be kept dry to avoid swelling and/or staining the wood facings. Structurewall panels should also be protected from moisture, because waferboard edges may swell slightly.

Protection from Moisture One of the major advantages of stresskin panels over earlier methods of insulating and finishing timber frame buildings is that the timbers are fully inside the insulated wall system and protected from moisture damage. With infill walls, on the other hand, moisture can migrate into the wall cavities where it can cause rotting of both timbers and intermediate studs. Nonetheless, moisture damage is still possible with stresskin wall systems, and precautions should be taken. Full protection from moisture damage calls for a two-part strategy: first, properly sealing panels during installation and second, controlling moisture in the finished house.

Figure 1. All panel joints must be sealed during installation. Apply a bead of expanding foam sealant in the pre-routed foaming channel just before abutting panels.

Sealing Panels During Installation
Improperly installed stresskin panels can allow moisture to move through the wall or roof, damaging the outer sheathing, siding, or shingles. All panel joints, corners, intersections and openings for windows and doors must be sealed with expanding foam sealant.
All panel joints must be sealed, whether or not they align with timbers. With panel joints that do not fall over timber supports, apply foam sealant in the pre-routed foaming channel as shown in Figure 1. Apply a heavy bead of high-expanding foam sealant in the groove of one panel just before abutting the adjoining panel to it. The foam will expand into the opposing groove to produce a tight seal.
When panels abut on posts or beams, you still must foam between them, even though splines are not required for strength. If panel edges are pre-routed for the dual 5/8 x 3" splines, these grooves must be filled, either with inset (nonstructural) splines, or with expanding foam sealant. Never leave routed grooves for splines unfilled. Apply foam in the foaming channel as with other panel joints. If abutting panel edges over timbers are not pre-routed, leave an intentional gap of 1/4 - 3/8" between panels and completely fill this gap with foam sealant after installation is completed.
Just as important as sealing between abutting panels is sealing other panel intersections. Always apply foam sealant where panels meet at corners, eaves, gable ends and ridge. These are the locations where the greatest air flow (and therefore moisture migration) can occur. Improper sealing at these points can lead to moisture damage of the outer wafer-board skin and exterior siding, as well as carpenter ant infestations. For the most effective seals at these points, leave an intentional gap between the adjoining panels and completely fill with expanding foam sealant later, At wall corners, for example, this requires installing the first panel 1/4 - 3/8" from the corner so that the overlapping panel will leave a gap, as shown in Figure 2. The same holds true where wall and roof panels meet and at the roof ridge.

Figure 2. At corners, hold the first panel back 1/4 - 3/8" and foam the gap later with expanding foam sealant.

Foam sealant should a!so be used where 2x4 splines are inset into panel edges at rough openings for windows and doors. Apply the bead of foam sealant just before inserting the spline, as shown in Figure 3. Even though the window or door unit will be foamed to the rough opening, the 2x4 edge spline must be foamed in place to prevent. air and moisture from migrating around it.

Controlling and Ventilating Moisture Almost as important as properly sealing panels during installation is the elimination of potential moisture sources from the house. Moisture elimination strategies involve both the builder (during construction) and the homeowner (after construction). During construction, pay a great deal of attention to the foundation wall and floor slab design. Follow accepted practices in waterproofing exterior foundation walls, assuring good drainage along the foundation walls (including porous backfilling and, where appropriate, specialized wall drainage matting), complete perimeter footing drains, and installation of a moisture barrier under a poured slab.

Figure 3. At rough openings for windows and doors, seal the reinforcing 2x4 blocking in place with a bead of expanding foam sealant.

Design a good ventilation system into the house. As a minimum, install exhaust fans in all bathrooms and the kitchen. A better option is to install air-to-air heat exchangers rather than exhaust-only fans in these locations. The best ventilation strategy is to install a whole-house air-to-air heat exchanger with ducts to bathrooms, kitchen and several other locations in the house. Air-to-air heat exchangers are superior io exhaust-only ventilation fans because they bring in and prewarm fresh air to replace the stale moisture-laden air being exhausted. Because the incoming air extracts heat from the outgoing air, air-to-air heat exchangers keep heating bills down while assuring a source of fresh air.
Finally, it is important that the homeowners not introduce large quantities of moisture into the house. Being careful about moisture sources in the house is particularly important during the first two to three years after construction, while the timbers and concrete are drying out and putting moisture into the air. Indoor relative humidity levels should not exceed 50%, and they should generally be kept under 40%. The precautions below can serve as examples and should not be considered all-inclusive:

• Do not store firewood in the house (including the basement); always vent clothes dryers to the outside;
• Never use unvented kerosene heaters in a house (along with releasing potentially toxic gases, these heaters produce large quantities of water vapor);
• Always operate kitchen ventilation fans or air-to-air heat exchangers when canning, boiling down syrups or otherwise generating a lot of steam;
• Avoid too great a density of house plants unless ventilation is provided.

Protection from Carpenter Ants Carpenter ants will occasionally take up residence in stresskin panels, digging out nesting cavities in the soft foam insulation. At best, carpenter ants are a nuisance; at worst they can reduce the insulation value of panels or even produce structural damage. Keeping carpenter ants out of stresskin panel-clad houses may require a multi-pronged approach. The strategies covered below should effectively discourage carpenter ants from establishing colonies in a house. Measures to be taken during construction by the builder, as well as ongoing measures to be taken by the homeowner, are covered. Following this is a discussion of how to find and get rid of an established carpenter ant colony.

Figure 4. Carpenter ants are the most common large (over ¼") ants found in houses. They can easily be distinguished from termites by their constricted bodies and bent antennae.

Preventing Carpenter Ant Infestations
During Construction:

1. Have the foundation treated with a long-acting residual insecticide before backfilling. Winter Panel recommends that you hire a licensed exterminator for all insecticide treatments.

2. Have the ground around the house treated with a residual-acting insecticide after backfilling.

3. Install a termite shield under the sill. Check with a building inspector in your area for recommended termite shield specifications.

4. Use pressure-treated lumber for sills and other areas where high moisture and rotting are likely.

5. Set stresskin wall panels on a bed of asphalt roofing cement rather than directly on the sill. This will discourage ants from entering between sill and panels and also reduce air and moisture migration under the wall panels.

6. Follow guidelines for stresskin panel installation discussed earlier in this information sheet to reduce air and moisture migration through panel joints, corners, intersections and openings for doors and windows. Careful sealing with foam sealant is required at ail such locations.

7. In wooded locations where carpenter ant infestations are particularly likely (especially where trees have recently been cleared), have the exterior sheathing and interior wall cavities treated with a long-acting residual insecticide. This will provide an extra measure of protection for the first year or so — until the house is occupied and moisture levels have dropped somewhat. The exterminator may be able to recommend a relatively safe insecticide for this purpose (especially interior wall cavities), such as a borax-based product.

Ongoing Measures by Homeowners

1. Avoid high humidity in the house. If relative humidity levels exceed 50% during the winter months, install air-to-air heat exchangers or other suitable ventilation strategies.

2. Keep the house clean. Carpenter ants do not eat woad or foam insulation — they eat insects, food scraps, garbage and other animal and vegetable matter. If you vacuum regularly, keep your kitchen tidy and prevent garbage from accumulating, carpenter ants will be less likely to take up residence in your house.

3. Do not stack firewood in your house or right against it. Many a carpenter ant colony has made its way into homes in firewood.

4. Avoid large flower beds and shrubbery right against the house. Try to leave 1½' of gravel or ground between vegetation and the house. Some old-timers recommend planting pansies to discourage carpenter ants.

5. Remove tree limbs that overhang the house.

6. Periodically inspect the sill for any gaps which may have opened up due to foundation settling or timber shrinkage and seal as necessary.

7. Maintain a regular treatment schedule with a licensed exterminator for the ground around your house. Depending on your location and the chemicals used, treatment may be required as often as every six months, though it is usually required just once every year or two.

Locating a Carpenter Ant Infestation
Determining if a carpenter ant colony has established itself in-your house is not always easy. Homeowners sometimes overreact after seeing a few ants and call in an exterminator when a problem does not exist. The sighting of a few carpenter ants during the summer or fall does not indicate that a colony has taken up residence in the house. Often, ants will nest outside in a rotted tree stump or other suitable location and enter your house only to forage for food. In the spring, it is not unusual to see occasional winged ants in the house (these are most likely young queens looking for nesting sites and should be killed).
If more than five carpenter ants are seen per day, however, chances are you have a colony living in the house. If you see carpenter ants in winter (in northern climates) there is almost certainly an infestation in the house, unless they were brought in with firewood.
Carpenter ant infestations in conventional wood-frame houses may go unnoticed for years, particularly if the ants forage for food outside. By the time the ants are discovered, they may have caused considerable damage. Stresskin panels, on the other hand, provide a sort-of built-in warning system. Because of their construction, with two rigid skins surrounding a foam core, you can often hear carpenter ants in panels. They make a distinctive rustling sound. While this may be alarming, it can be a big benefit, allowing you or an exterminator to pinpoint the colony location precisely with a stethoscope and eliminate it.
Small piles of sawdust, shavings or foam (called "frass") provide another good indicator of a nesting colony. Carpenter ant frass has a shredded quality, somewhat resembling pencil shavings, and it will usually include insect fragments. (Sawdust from powderpost beetles and termites — other common pests in wood — is much finer because the wood has been digested.) Even with a sizeable carpenter ant colony, you may not see any frass, however, because it is often deposited in hollow cavities out of sight.
If you suspect carpenter ants, look in areas where rotting is likely: sills, window casings, at wall corners, around windows, along the roof ridge and eaves, under leaky pipes, etc. Listen for them and look for piles of frass. The ants may actually do you a favor by leading you to areas of moisture damage requiring repair.

Getting Rid of Carpenter Ants
Winter Panel recommends hiring a licensed exterminator to rid a house of carpenter ants. A wide range of quite toxic and potentially dangerous chemicals are used for their control. The work is best left to professionals. Because a carpenter ant colony in stresskin panels can often be precisely located, control can be accurately targeted and very effective with a minimum of insecticide. After locating the colony with a stethoscope, the exterminator can drill small-diameter holes through the panel skin into the colony and inject a contact insecticide.

Radon Control
Over the past few years, radon has emerged as a significant concern in houses nationwide. The colorless, radioactive gas seeps into buildings primarily through basement walls and floors. The U.S. Environmental Protection Agency (EPA) considers radon to be a leading cause of lung cancer, responsible for as many as 20,000 deaths a year. In tight, energy-efficient houses, radon levels can build up because indoor air is not replaced with fresh outside air as frequently as in looser houses.
EPA recommends that radon levels should not exceed 4.0 picocuries per liter of air (pC i/I). When radon levels are higher, measures should be taken to bring them down. New houses should be designed and built both to minimize the likelihood of elevated radon levels and to simplify radon reduction measures if they are called for in the future. Winter Panel supports these efforts and offers the following guidelines to help you design and build a radon-safe house.

1. Minimize Radon Entry Into the House
Strategies to reduce radon entry into homes primarily involve sealing the basement walls and floor. These measures include: installation of a polyethylene moisture barrier under the basement floor slab; installing expansion joint material where basement slab and walls meet; removal of grade stakes after pouring basement floor; sealing any cracks, holes and penetrations in the basement floor and walls with a suitable caulk, such as polyurethane; installing tight-sealing covers on basement sumps; and waterproofing the outside of foundation walls. Where possible, build with poured concrete foundation walls rather than hollow block.

2. Design House to Avoid Negative Pressure
If a house is under negative pressure, it will tend to pull radon in through any entry points in the foundation walls and floor. You can minimize the likelihood of negative pressure by providing outside combustion air for all combustion appliances, including furnaces, boilers, wood stoves, fireplaces, gas water heaters; providing make-up air for clothes dryers; using air-to-air heat exchangers rather than exhaust-only fans for bathroom, kitchen and other ventilation requirements; and keeping the building envelope tight, especially eliminating air leakage through the roof, which can result in the stack effect, pulling air out of the house.

3. Design House to Simplify Future Radon Mitigation
Radon levels vary greatly from region to region and even from building site to building site in the same location. High radon levels can occur in houses in some cases even if the above guidelines have been followed. For this reason, you should incorporate features into houses that will facilitate future radon mitigation (removal) if high levels are found.
Install 4" of tamped clean aggregate (pea gravel or larger) under the slab. Before pouring the slab, install a 4"-diameter plastic "standpipe" into the subslab gravel. This should extend about one foot above the slab floor and be capped off. If future radon mitigation is required, this pipe can be extended up through the roof or foundation wall and fixated with an in-line fan to pull air (and radon) out from under the house. Label the standpipe to avoid future confusion. Also, after waterproofing the outside wall, install footing drains and backfill with clean aggregate. If necessary, the footing drain outlet pipe(s) can later be fitted with a trap and in-line ventilation fan to depressurize the area around the foundation wall.

For More Information
The Winter Panel sales and technical staff will be glad to answer any questions you have on these and other issues relating to the proper installation of stresskin panels. For recommended installation procedures for stresskin panels on timber frame buildings, also refer to the Timber Framer's Guide to Stresskin Panel Installation, published by Winter Panel.