Can Romex cables be routed through panel chases without metal conduit under standard residential electrical codes?

Under National Electrical Code Article 334, standard NM-B Romex cable can run directly through continuous insulation panel chases without metal conduit, provided the wiring sits behind approved half-inch drywall and meets standard depth protection rules.

In basements, container homes, and masonry retrofits across the United States and Canada, framing traditional wood or metal stud walls solely to route electrical wiring consumes up to 3.5 inches of interior perimeter space and creates severe thermal bridging. Continuous insulation panels with integrated electrical raceways eliminate redundant stud framing while maintaining compliance with residential building codes, including the International Residential Code and National Electrical Code.

If you only do one thing: Verify that your routed NM-B cable sits at least 1.25 inches back from the face of the panel framing studs to comply with NEC 300.4 without requiring steel nail plates.

1. Plan raceway alignment: InSoFast expanded polystyrene (EPS) panels feature factory-molded horizontal chases at 16-inch intervals and vertical chases at 24-inch intervals, forming a continuous utility grid across the entire wall assembly for pulling 12-gauge or 14-gauge NM-B wire.
2. Cut electrical box openings: Use a utility knife or multi-tool to cut a standard 2.25-inch by 3.75-inch opening in the foam for plastic work boxes, anchoring the box directly to the concrete or masonry backing with masonry screws or approved adhesive.
3. Pull Romex through chases: Feed unshielded NM-B cable through the engineered chases from ceiling drops or floor transitions, routing wires cleanly through intersecting channels without stripping the outer jacket inside the foam.
4. Maintain setback distance: Keep conductors seated fully inside the panel channels at least 1.25 inches behind the stud face, ensuring standard 1-5/8-inch drywall screws driven into the embedded studs cannot pierce live wires.
5. Install approved thermal barriers: Fasten minimum 1/2-inch gypsum drywall (or 5/8-inch Type X where required) directly to the panel studs, fulfilling the mandatory 15-minute thermal barrier required by IRC Section R316.

• Watch out for: Local municipal amendments in jurisdictions such as Chicago that mandate metallic conduit (EMT) or armored cable (MC/AC) regardless of standard residential code exemptions.
• Watch out for: Stripping cable sheathing inside the EPS insulation chase rather than inside the junction box, which violates NEC 300.14 conductor containment requirements.
• Watch out for: Securing outlet boxes solely with expanding spray foam without mechanical anchoring to the underlying substrate or embedded stud flange.

Map your branch circuit layout and submit your panel schedule to your local electrical inspector to confirm local NEC Article 334 adoption before roughing in boxes.