How to Install Dow Tuff-R Commercial Insulation

Dow TUFF-R insulation is rigid polyisocyanurate foam with a radiant aluminum barrier on both sides.

The double barrier means that a 1-inch thick panel provides an insulation factor of R 6. 5, as opposed to R 5 for the same thickness of regular foam. In addition, the barriers eliminate the need for any additional vapor barriers. This simplifies the installation process on wood-frame homes.

Mark the length to which each panel needs to be cut by dragging the tip of a tape measure through the surface of the panel. This leaves a small line to use as a guide.

Set the panel on a pair of sawhorses and draw the utility knife blade through the line in the panel. Make a deep score in the foam -- don't cut all the way through.

Line the score in the panel with the edge of the sawhorse and push down on the short end of the panel; it will snap off cleanly at the score.

Place the panels vertically up against the studs of the house. Drive nails through the panel and into the studs -- spaced 12 inches apart around the outside of the panel and 16 inches apart in the middle of the panel.

Place subsequent panels so that they butt firmly against the panels next to them. Seal the joints between panels with insulation tape.

Seal any areas where vents, ducts and other structures must pass through the foam panels with all-weather sealing caulk.

Siding, or stone or brick veneer, should be installed over the TUFF-R.

Things You Will Need

  • TUFF-R panels, 4 foot by 8 foot, or 4 foot by 9 foot
  • Tape measure
  • Sawhorses
  • Utility knife
  • Ring shank nails, 1 1/4 inch long
  • Hammer
  • 3-inch insulation tape
  • All-weather sealant


  • The panels should cover all structural elements of the house, including any corner bracings.
  • The panels can be easily trimmed around protrusions with a utility knife and straight edge.
  • TUFF-R can also be installed on interior masonry walls, but usually unfaced or single-faced foam panels are specified for these applications.


  • Your local building code authority may require a different fastening procedure than is described here. Always check your local code for the proper installation requirements for rigid foam insulation.

About the Author

Scott Knickelbine began writing professionally in 1977. He is the author of 34 books and his work has appeared in hundreds of publications, including "The New York Times," "The Milwaukee Sentinel," "Architecture" and "Video Times." He has written in the fields of education, health, electronics, architecture and construction. Knickelbine received a Bachelor of Arts cum laude in journalism from the University of Minnesota.