MAX 3.75 R-15.9 InSoFast Panels

The MAX-3.75 – 6 panels per box has a coverage of 48 sf, and has a minimum order of 4 boxes. For smaller projects, check out our MAX-3.75 – 3 panels per box. 

The MAX 3.75 Panel is a 3¾‑inch insulation panel that delivers R‑15.9 continuous insulation with built-in studs/furring strips. Its injection‑molded, closed‑cell EPS core is non‑toxic and inert, retains its R‑value for the life of the building, and is rated for above or below‑grade use such as exterior walls or basements. The panels carry a Class A fire rating and function as a Class III vapor retarder, providing a durable thermal and moisture control layer for new construction and retrofit projects.

The Max 3.75 Panel will never rust, rot, mold or decay and has drainage channels on both sides of the panel to allow drainage and drying of the wall assembly. For exterior applications, this means that water that infiltrates the wall can drain down both sides of the panel, prevent water from being held in tension inside the wall. For basement applications, the back side drainage channels allow water that infiltrates the foundation wall to drain down the back side of the panels, limiting damage. If water infiltration is expected, the panels can be flashed into a french drain.

Each panel is molded with Built-in high‑strength polymer studs aligned 16 in O.C., creating a load‑bearing structure for drywall, exterior finishes, cabinets, and more. The stud’s front faces are fully embedded beneath the face of the pane ½‑inch to provide a double thermal break when attaching the panels with screws, while the back side of the studs feature ribbed dovetails for adhesive attachment to concrete, stone, metal, or brick. Because the studs are non‑conductive and resistant to moisture damage, they prevent thermal bridging and maintain a stable substrate for finishes.

The tightly interlocking tongue‑and‑groove edges form a continuous, self‑flashing seal, eliminating the need for traditional foamboard tapes, and preventing water from penetrating through the panels. A notched alignment system keeps panels and studs aligned during installation, and marking on the front of the panels show screw patterns and electrical raceways for fast, accurate layout.

Sealed electrical raceways run vertically at 16 in O.C. and horizontally at 24 in O.C., creating a code‑approved grid that simplifies pulling wiring to any location and provides the required separation from the face of the panels to protect electrical wires. Electrical rough-in is quicker than traditional framing, with no need to drill holes through studs to run electrical wires. 

Attachment Methods:

Construction Screws: 4 1/2″ #9 or larger construction screws into wall framing spaced at 12″ O.C. along the InSoFast stud. (6 per panel)

Loctite PL Premium 3X Construction Adhesive: apply a 3/8″ diameter bead of adhesive on the three black glue strips on the back of the panel, then press in place. (1 28 oz tube per 6 panels)

Shipping & Returns

Click HERE for shipping details & return policy

Order a Sample

Click HERE to order a sample pack that includes all of our InSoFast Panels!