How to Use PolyIsocyanurate Insulation

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  • 6-8 hours
  • Intermediate
  • 500-700
What You'll Need
Polyisocyanurate insulation
Vapor barrier
Plywood sheeting
2x2 or 2x4 framing studs
Utility knife
Concrete adhesive
Measuring tape

PolyIsocyanurate insulation is a type of insulated foam board that offers a high level of thermal resistance and cold weather protection for your home. Polyisocyanurate insulation costs more than other types of foam board but can help to save you thousands of dollars in electrical heating and cooling costs. Installing and using polyisocyanurate insulation is not that difficult; however, there are a few things you should do during the installation to make the insulation more effective. This simple how-to guide will provide you with some steps you can use to make installing polyisocyanurate insulation in your home easier and more energy efficient.

Step 1 - Cut With a Utility Knife

If you need to cut sheets of how the polyisocyanurate insulation, you should use a utility knife rather than a drywall saw or other type of cutter. When cutting the material, use a straight edge and cut on the side of the foam board that has the foil surface attached (if applicable). Snap the foam board rather than trying to cut all the way through it.

Step 2 - Use Adhesive to Attach Foam Boards

Never use nails or staples when installing polyisocyanurate insulation. Instead, use a quality contractor adhesive to glue the foam boards in place. It doesn't matter if you're attaching the foam boards to cement walls in the basement or installing them in rafters of a ceiling, use adhesive to attach the sheets of foam board insulation.

Step 3 - Always Install Vapor Barrier

Moisture can easily damage polyisocyanurate insulation. Therefore, you should always install a vapor barrier between the piece of insulation foam board and the exterior wall where it is installed. When installing a vapor barrier, it is better to attach it to studs or the wall material rather than gluing it directly to the insulation. When choosing a vapor barrier, choose one that is as resistant to moisture as possible. Moisture that reaches the insulation foam boards will quickly reduce the R-rating for the insulation and make it less efficient in providing cooling and thermal protection for your home.

Step 4 - Frame in Cement Walls

Because you won't be able to nail or staple to the surface of polyisocyanurate insulation foam boards, you will need to frame in cement walls in basements where you install the insulation. To do this, you can use 2 x 2 inch pieces of lumber to create frames that you can then attach drywall and a moisture barrier to in order to cover the foam boards.

Step 5 - Cover with Drywall or Paneling

It is also not a good idea to leave the insulation uncovered. So, always frame in the walls where the foam boards are installed and cover with drywall or even wood paneling. Again, always ensure that there is a vapor or moisture barrier between the insulation foam boards and the covering material.