Standard Box Install Procedure (Plywood + Insofast)
This method ensures a secure, airtight electrical box installation while preserving the integrity of your insulation and air barrier layers.
Installation Steps:
- Mark box location between 40–44" above finished floor, aligned with a vertical Insofast chase.
- Cut through the ¾" plywood at box location using a multi-tool or jigsaw.
- Optional: If needed, shave 1/8"–1/4" into EPS to fit the box depth. Avoid disturbing the chase or Insofast studs.
- Drill a small hole through the EPS behind the box into the Insofast chase. Drop Romex through.
- Pull wire through into the box cavity, leaving enough slack to work comfortably.
- Apply low-expansion spray foam around the box opening (back and sides) and seal the wire entry.
- Secure the box to the plywood with screws. Ensure the face is set to finish flush with drywall.
- After drywall, use a box extender if needed, and install cover plate with a foam gasket for extra air sealing.
Wall Section Summary:
| Interior Room | ----------------------------- | 1/2" Drywall | | 3/4" Plywood (box mounts) | | 2.5" Insofast EPS (R-10) | | Concrete/Masonry Wall | ----------------------------- | Exterior |
Shopping List for Outlet Install (Home Depot)
- ✔️ Shallow plastic or metal boxes – 1.25" to 1.5" deep (e.g., Carlon 14 cu in)
- ✔️ Box extenders / mud rings – to bring boxes flush to drywall(later)
- ✔️ Low-expansion spray foam – e.g., Great Stuff Pro (we have)
- ✔️ Fire-rated putty pads or acoustic sealant (Tremco)
- ✔️ Foam outlet gaskets – for air sealing behind plates(later)
- ✔️ Screws for securing boxes to plywood (rated for plastic/metal boxes)
Pro Tip: Keep outlet height consistent with a chalk or laser line at 42" for a modern, accessible layout.