Overview:

Our wall system has many benefits compared to stress skin panels. There are many types of wall panels and many different terms (stress skin, structural insulated panel, foam core, sandwich panel and many others) for similar products. Most of the systems consist of two outer skins (typically oriented strand board) and one inner core of insulating material to form a monolithic unit. For ease of explanation we are going to use the term "stress-skins" for comparison to our wall system.

Stress skin panels look like they are a complete and easy solution for use as a wall system. Unfortunately, there is a lot more to a wall system than just insulation and ease of installation.

Nail Base:

One of the major issues is that most stress skin panels do not have any solid material to use as a nail base (they are filled with foam). The Western Red Cedar Lumber Association specifies that nails must penetrate 1 ½" into solid wood, otherwise the siding can cup and pull out the nails which will also ruin the paint job (trim is also an issue). On the interior of the home, there is no solid nail base for attaching items such as your upper kitchen cabinets and large pictures or other wall hangings. With our wall system, there are solid wood studs into which nails can be attached.

Wiring:

Not all stress skin manufacturers include wiring chases, and if they do, all of the wiring must be done through an existing chase, making it time consuming and difficult. All outlets and switches must be in predetermined locations, otherwise insulation must be melted out of the panel, compromising the integrity of the panel’s energy efficient properties and increasing labor costs. Also, future communication and electrical upgrades can become difficult or impossible. Please note that plumbing has many of the same issues. Our wall system uses open framing so that wiring and plumbing can be run like a conventionally framed house.

Bugs/Rodents:

Bugs and rodents have been found to burrow into the expanded polystyrene (not the extruded polystyrene that we use), compromising integrity and insulation value of the panels and creating a host of other issues. "A few cases have been noted where insects and rodents have tunneled throughout the SIP’s" (U.S. Department of Energy, consumer energy information: EREC Briefs).

Cost:

Not only are the panels themselves fairly expensive, but you will also pay more for some of your subcontractors. Due to the difficulty of working with stress skin panels (as mentioned above) many contractors will produce higher bids. Also, "... The tendency for any subcontractor asked to bid on unfamiliar spec’s is to throw a high number at the job to cover the unusual." (Building with Structural Insulated Panels (SIPS) by Michael Morley p. 140). Our system is inherently more cost efficient.

Condensation:

Both our wall system and stress skin panels handle condensation very effectively by providing a complete thermal break from the framing, resulting in less chance of condensation compared to conventionally framed wall systems.

Air Infiltration:

Both our wall system and stress skin panels do not allow as much air leakage (drafts) as a conventionally framed wall system. Our wall is built in layers so joints are staggered. With stress skin panels, joints line up through the entire panel, so if the manufacturer uses a poor sealing technique, or if the installer does not follow the directions closely and the seal between the panels fail, major air leakage (drafts) can occur.

R-Value:

Stress skins are available in varying thicknesses and types of foam core resulting in a wide range of R-values. Most stress-skin manufacturers advertise similar R-values as our wall system and 2x6 walls with high-density fiberglass. You can easily specify higher R-values, but that may not be the best place to spend your money (you can increase conventional wall R-values as well). You can more effectively increase thermal performance of your home and make it more comfortable by putting the money into additional roof insulation or higher quality windows, where more heat is lost than through the walls.