Sample Installation Image

Polyiso is a closed-cell, rigid foam board insulation used primarily on the roofs and walls of offices, health facilities, warehouses, retail and industrial manufacturing facilities and educational institutions. Because of its high thermal performance, it is the product of choice for energy-aware homebuilders and consumers.


  • Shall conform to ASTM C1289.
  • Come in many thicknesses to accommodate almost any end use.
  • Highest R-value per inch of any foam plastic insulating sheathing.
  • Lightweight, easy to install. Easily cut to fit with a utility knife.

Exterior wall coverings are attached:

  • Directly through the Polyiso to framing below.
  • Into furring attached through the Polyiso to framing.

Shall be installed in accordance with:

  • Code compliance requirements per TER 1410-08.
  • Manufacturer’s installation instructions.
  • The following general installation guidelines.

Step 1

Verify Polyiso and Framing

  • Polyiso must have minimum compressive strength of 15 psi.
  • Must comply with ANSI/SBCA FS100 where wind pressure resistance is required.

Note: Wind speeds shown in Table 1 are VASD. Where VULT is used, multiply wind speeds by a factor of 1.26.

  • Wood framing may be any softwood species with specific gravity 0.42 or higher.
  • Steel framing must be:


Step 2

Verify Fasteners

  • Exterior coverings may be attached by the following methods:

(a) Cladding
(b) Fasteners
(c) Furring
(d) Polyiso
(e) Framing
(f) Cavity Insulation
(g) Interior Wall Finish



  • Fasteners must meet penetration requirements per IRC Table R703.3(1) into:
    • Studs
    • Framing members
  • Where penetration into framing is not required, fasteners must extend 1/4" beyond the opposite face of the sheathing per IRC Table R703.3.2.

Step 3

Place Insulation Boards

  • Ensure wall is square and true.
  • Align boards with bottom edge of wall.

  • Verify stud spacing, blocking and bracing requirements per manufacturer’s installation instructions.
  • Provide framing or blocking for attachment of siding and trim at transitions. (Seams should not be visible from interior unless allowed by manufacturer.)

Step 4

Attach Insulation Boards

  • Space fasteners per manufacturer’s installation instructions:
    • Around edges of panel.
    • Through panels and into interior members.

  • Drive nails flush and snug.
  • Do not overdrive nails.
  • Do not underdrive nails. (Exception: Leave 1/32" gap [or as required by manufacturer's installation instructions] to allow for lengthwise thermal expansion of vinyl or aluminum siding.)

Step 5

Trim Boards at Openings

  • Trim boards at all window and door openings.
  • Cover all framing with Polyiso.
  • Fit joints tightly.

Step 6

WRB and Flashing

  • Ensure that a code-compliant water resistive barrier (WRB) and required flashing is provided.
  • If using Polyiso as a WRB, seal all joints and openings and penetrations per manufacturer’s installation instructions.

  • At pipe and other small penetrations, seal gaps with silicone or expanding spray foam sealant.
  • Seal joints and openings with joint tape per manufacturer’s instructions.

  • Repair damaged areas per manufacturer’s installation instructions.