Exterior Installation

The InSoFast EX 2.5 Panel is optimized for exterior usage. If you choose to use the InSoFast PLUS method with additional sheet foam or the UX 2.0 panel, please note that drawings, instructions and images referenced by this guide and in several other locations across this website will likely assume the use of EX 2.5 panels and refer to its 2½” thickness.

Project Estimation

InSoFast panels are generally estimated the same as siding. Take the total square footage of all walls less openings. Calculate openings with 6″ of waste on all sides.

Gable end square footage can be estimated by adding 2′ to the height and width.

Do not overestimate. Miscut panels can be glued back together and reused.

Tools and Supplies

  • Screw gun
  • (optional) Nail gun
  • Long snap off blade utility knife
  • Saw – hand, jig, skill, table
  • Gap and crack foam for sealing corners/openings and at the top of walls


InSoFast panels should be attached to the structural wall or sheathing after the installation of a weather resistant air barrier (WRB). All openings, penetrations, extensions, etc should be properly flashed, sealed and integrated into the WRB before InSoFast panels are installed.

The WRB products should be installed according to industry standard practices and are independent of InSoFast insulation panels.

Basic Installation Procedure

Orientation of Panels

The word “InSoFast” must face outward toward the installer with the exposed ribbed side of the studs going against the wall or sheathing. No black strips will be visible.

InSoFast panels are installed with the 4’ width dimension running horizontally. The 2’ height dimension, studs and moisture control channels all runs vertically.

The top edge of the panel features the interlocking tongue and the bottom edge features the interlocking groove.

Bottom of the Wall

Snap a straight line for the starter track or flashing at the bottom of the wall so that the bottom of the InSoFast panel is not exposed.

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Running Bond Pattern

For long walls, installation can be expedited by starting at a centered position with a full panel and working outward in both directions

Stagger panels on the second and subsequent rows to form a running bond interlock pattern.

When cutting panels for corners, openings and penetrations, leave a ¼” gap to fill with foam sealant.

For easier installation, do not install the upper row of fasteners in the InSoFast panel until the panel above has been set in place

Top of the Wall

Prior to installing the top row of InSoFast panels, apply a continuous bead of sealant to the sheathing at the top plate line of the wall.

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Installing Panels over Framed Walls

Screw/Nail Attachment Pattern

Per code report, screws are to be places 12″ O.C. along the InSoFast studs.

InSoFast panels are generally screwed in place, however, you may opt to use nail guns to install the panels and siding provided the temperature is above 60 degrees F for the stud to accept nails. It is up to the contractor and/or building official to determine the suitability for the use of and spacing of nails.

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For 16” O.C. Framing

InSoFast studs are 16” O.C. Install the first panel so that the built-in studs line up with and attach to the wall’s studs.

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For 24” O.C. Framing

Attaching to 24” O.C. framing requires a screwable structural sheathing, such as OSB or plywood. The number of screws is dependent on your wind load requirements.

Installing Panels over Concrete or Masonry Walls

Adhesive Attachment

We have tested and recommend PL Premium 3X Construction Adhesive® for bonding to the InSoFast studs. Other formulas and brands may not work as expected. Cure time is dependent on temperature and humidity. Ensure sufficient time for the adhesive to set and cure before attaching exterior finishes. In colder temperatures, cure times are extended. See adhesive data sheet for more information.

On the back of the panel, apply a 3/8″ bead of PL Premium 3X Construction Adhesive® along the dove-tailed ribbing of each InSoFast stud. Rougher or uneven surfaces may require a thicker bead.

Press panels firmly into place against the wall. On windy days, the panels may need supplemental bracing or mechanical attachment to secure the panels until the adhesive has set.

Mechanical Attachment

If you choose to mechanically attach InsoFast panels to concrete or masonry walls, screws are to be placed 12″ O.C. along the InSoFast studs. Powder actuated tools are not recommended.


Outside Corners with Backing

One option is to install 2x lumber with 1″ foam board added to provide a solid 2½” thick backing as needed.

Outside Corners with No Backing

Overlap the panels past the corner by the thickness of the panel (i.e. 2½” for EX 2.5) creating an overlapping butt joint. Leave a ¼” gap at the butt joint for foam sealant.

Corner posts can be attached with 4″ screws directly back to the framing when an InsoFast stud is not located near enough to the corner for siding attachment.

Sheet metal flashing may be added behind the corner post for siding fastening at the corner post

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Inside Corners

Butt InSoFast corners together, leaving a ¼” gap at the butt joint for foam sealant.

Install metal corner flashing to provide attachment for the corner post and siding.

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Windows and Through-Wall Penetrations

Install all windows, flashings and penetrations as per each manufacturer’s installation instructions.

Outset Windows

An outset window is installed with nailing flange flush with the front face of the InsoFast panel.

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Inset Windows

An inset window is installed with the nailing flange flush with the exterior sheathing layer of the wall requires sill and jamb extensions for the exterior.

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Other Through-Wall Penetrations

Mechanical penetrations are treated as they would be for typical construction.

All through-wall penetrations should be installed and sealed back to the WRB layer before the InSoFast panels are installed.

Cut and fit the InSoFast panel around the penetration, leaving ¼” gap. Fill the gap between the penetration and the InSoFast panel with a foam sealant.

Installing Exterior Finishes


InSoFast panels can be used with virtually any type of siding or cladding. The panels are rated for up to 2″ thick adhered stone or brick.

For all finish types, please refer to the finish manufacturer’s installation instructions for fastener size and spacing.

Fastener Selection

Use corrosion-resistant fasteners long enough to penetrate 1″ into the embedded InSoFast stud.

You can opt to use nail guns to install siding. This is only recommended when temperatures are 60 degrees. Smaller nail size and shank diameter will perform better at lower temperatures. It is up to the siding manufacturer, contractor, and/or building official to determine the suitability for the use of gun nails when installing siding.