10 Best Practices for Installing Owens Corning XPS Insulation

XPS insulation like Owens Corning® FOAMULAR 250® plays an important role in boosting a home's or building's energy efficiency. But like any material, performance relies on proper installation of both the product and those around it.

First and foremost, always follow manufacturer instructions for installing XPS insulation as well as for the compatibility of products it will come in contact with. Following that, here are a few best practices to consider to ensure your insulation is installed properly.

XPS Insulation for the Slab

1. When using insulation to insulate the slab, it's a good idea to consult an engineer; each foundation has different point loads to consider, and their expertise can ensure the right products and methods are specified.

2. FOAMULAR is lightweight, which means it could blow away if things get windy. Use a small piece of tape to hold the boards together before the concrete is poured. If not pouring right away, add weight to perimeter boards.

3. To reach a specific R-value, you may want to stack boards. Always off-set the seams for multiple layers of Foamular. The same is true for the polyurethane (poly) that will go on top-seal and overlap any seams by about a foot to keep out soil gasses.

Below-Grade Foundation

4. Unlike some materials, FOAMULAR 250 boards can bebutted together tightly. Seams do not need to be taped in below-grade applications since the Foamular is not the water barrier.

5. You'll need adhesive to adhere the boards to the wall-ensure your adhesive is compatible. Verify on the package and ask the manufacturer when in doubt. Failing to do so could cause the XPS to degrade.

Above-Grade Walls

6. If using cap nails, ensure the washers do not overlap. Doing so will not allow the boards to join properly and can create issues with water and air. Employ a staggered nailing pattern for the seams.

7. Instead of using housewrap, taping XPS board seams in above-grade applications can provide an air and water barrier. For FOAMULAR 250, only use Home SealR®, JointSealR®, or FlashSealR® as required by Owens Corning. This ensures the products are compatible with the proper certification testing.

8. Apply pressure to the tape using a J roller; this will activate the adhesive as well as help eliminate air bubbles to keep things air tight.

9. If you don't want to tape the seams, include housewrap under or over the XPS sheathing, which will add the air and water barrier the tape typically would normally provide. Just be sure that the flashing for penetrations is on the same plane as the housewrap.

Jobsite Storage

Along with proper installation, proper storage also is key to preserving performance of XPS insulation board. FOAMULAR 250 is delivered in a protective wrap to avoid UV degradation. If you open a unit, make sure the wrap stays intact and re-cover the product as soon as possible.

For more information and tips, visit Owens Corning's product page.
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