With Additional Bracing, Styrofoam Can Serve as Sheathing Without OSB Panels
The key is to install alternative wall bracing, either “let-in” or metal strapping to meet code-mandated structural requirements.
Tremendous demand and supply chain interruptions have caused the price of OSB to shoot up by as much as 100 percent over pre-pandemic prices.
OSB Replacement. Styrofoam Residential Sheathing offers a lightweight, efficient sheathing alternative to high-priced OSB panels.
One solution: Specify rigid Styrofoam Residential Sheathing instead of OSB, for sections of the home that can be brought to code with other stiffening measures. Essentially you’re pre-strengthening the wall, so the insulating panels can perform their primary function: reducing air infiltration and greatly improving building performance.
According to DuPont, the manufacturer of Styrofoam, “The weatherization can be completed by covering the Residential Sheathing with a water- and air-resistive barrier, like DuPont Tyvek HomeWrap, allowing for windows and penetrations to be fully integrated to the weather barrier.”
Resources: Here’s an article from Fine Homebuilding on four ways to brace a foam-clad exterior.
If the Styrofoam is installed this way, it addresses a key envelope “weakness” that OSB alone does not: thermal bridging. As a result, it can boost the R-value of exterior walls by up to 20 percent. Also, by reducing the total amount of heat moving through a wall, the product makes condensation inside the wall cavity far less likely. In some climates, moisture trapped in wall cavities can be a major cause of mold or mildew growth.