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Wiring an ICF House: Boxes on the Webs, Cable in the Foam, Sleeves Before the Pour, and the Penetration List That Saves You a Core Drill
Electrical & Lighting
Wiring an ICF House: The Wire Is Easy, the Holes Are Not
I have built ICF houses since 1995, and the electrical is not the hard part. The foam cuts like a birthday cake and the webs give a box something solid to hold. What catches people is the concrete in the middle. Anything that has to pass through the wall has to be planned before the pour, because afterward the only tool that works is a core drill. This page covers how an ICF wall gets wired, the list we walk before every pour, and what the inspector wants to see.
How the Wall Gets Wired
An ICF exterior wall is two layers of foam held apart by plastic or steel webs, with concrete poured in the middle. The webs are moulded into the forms on a regular spacing and show up on the face of the foam as furring strips. They are what the drywall screws into, and they are what the electrician fastens the boxes to.
The cable runs in a channel cut into the inside face of the foam with a hot knife or a router, at the depth the code requires, and then it is protected where the code calls for it. The interior foam is the insulation on that side of the concrete, so a sloppy two-inch gouge is a little cold stripe in your wall forever. A good electrician cuts the channel just deep enough and no deeper.
Interior walls in our houses are ordinary wood frame and are wired the ordinary way. The ceiling is usually frame too, unless it is a concrete deck. So the ICF part of the job is really the outside walls: the receptacles along them, the switches beside the exterior doors, and everything that goes through to the outdoors.
If you have never seen one of these walls, the what are ICFs page shows the form, and the ICFPro.ca site covers the walls and foundations from the contractor’s side.
What It Costs Extra
Less than people expect. The electrical package for an ICF house is priced the same way as any new house, by the square foot with the add-ons, and the cost to wire a house page has those numbers. Cutting channels in foam is not slow work, and an electrician who has done a few ICF houses has little reason to price one far above frame. One who has never seen one may price the fear. Ask how many they have wired.
| Item | When | Cost |
|---|---|---|
| Complete wiring package, new house | rough-in and finish | $8 to $12 per sq ft |
| Sleeve set in the form | before the pour | a piece of pipe and a few minutes |
| Core drill through a poured wall, with the patch | after the pour | $150 to $400 a hole, allowance |
| EV-ready 240 V circuit | rough-in | $750 to $1,200 |
| Same EV circuit added after drywall | later | $2,000 to $2,800 |
| AC or heat pump circuit | rough-in | $300 to $600 |
| Generator inlet | rough-in | $700 to $1,200 |
| Hot tub 50 A GFCI circuit | rough-in | $750 to $1,100 |
October 2026, before HST. The add-on prices are from an Eastern Ontario licensed contractor’s published new-build list. No contractor we found publishes an ICF premium, so we do not show one.
Why Ontario prices are all over the map: the contractors and price guides we checked for new-house wiring quoted very different prices for the same job, and none of them priced ICF separately. An Ottawa electrical contractor said $4 to $7 a square foot, a London contractor $6 to $8, and an Eastern Ontario contractor about $9 to $10.50 with the underground service and permit in. On 2,000 sq ft that is $8,000 to $24,000. The gap is scope: the service, the permit, the exterior and appliance circuits, the fixtures. Budget $10 a square foot, and get two or three quotes on the same written scope, with the penetration list attached.
The Penetration List: Every Hole, Before the Pour
A frame wall forgives you. Forget a hole and the electrician drills one through the sill plate in five minutes. A poured wall does not forgive anything. Forget a sleeve and it is a core drill, $150 to $400 a hole with the patch, plus the trip, plus a day of somebody looking at you.
So before every pour we walk the house with the electrician, with this list in hand, and mark every sleeve on the forms:
- The service entrance: where the underground conduit or the overhead mast comes in, and the meter base location.
- The outdoor unit: the line set and the 240 V feed for the heat pump or AC.
- Exterior lights: beside every door, the garage, the deck, any wall-mounted floods.
- Exterior receptacles: front, back, deck, garage side, and one where the Christmas lights will go.
- Hose bibs, for the plumber, while you are at it.
- Dryer vent, range hood vent, bathroom fan exhausts that leave through the wall, and the HRV hoods.
- The generator inlet, if there is one now or might be one later.
- An EV charger feed to a detached parking spot or post.
- Low voltage: a camera, a doorbell, a gate, a sleeve for whatever comes next.
Say the list comes to 16 sleeves and three get forgotten. At the middle of our allowance, 3 x $275 = $825 in core drilling, before the patch is painted to match. A spare sleeve or two in the likely spots costs almost nothing. Capping an unused sleeve beats renting a core drill.
Rule of thumb: if it goes outside, it gets a sleeve. If you are not sure whether it goes outside, it gets a sleeve.
Lights and Receptacles on a Concrete Wall
An exterior light needs something solid to screw to. The outside of an ICF wall is foam with the finish over it, stucco, siding or stone, and a fixture fastened to foam alone will crush it and lean. A good crew sets a mounting block or plate at each light and receptacle, tied to the webs, before the finish goes on, so the box sits flush with the finished face and the fixture has something to bite.
Outdoor receptacles within 2.5 m of finished grade need GFCI protection under the Ontario Electrical Safety Code, 2024 edition, which has been in force since May 1, 2025. That edition also added outdoor receptacle requirements for single dwellings, so ask your electrician where they want them before the forms go up, not after. A receptacle you decide on in July is a sleeve you needed in May.
The rough-in walkthrough for the rest of the house, the inside walls and the ceilings, is on the before-drywall checklist.
What the Inspector Looks At
The ESA inspector sees the rough-in like any other house: the boxes secured, the cable supported and protected where it runs in the foam, the right wire on the right breaker, and the box fill. Nothing gets covered by insulation or drywall until ESA authorizes it. On the ICF outside walls the insulation is already there, so the thing that gets covered is the drywall, and the drywall crew waits for the inspection like everyone else.
On our builds the electrical is done by the licensed electrical contractors we hire, under their licence and their ESA notification. I do the coordination, the walkthrough and the list; they do the work. If you are building your own ICF house, whoever you hire for the wiring must be an ESA Licensed Electrical Contractor. You can do the work in your own home yourself, but then you file the notification before you start and you pass the inspection, the same as anyone.
One more thing an ICF house changes: the service. A tight ICF house has a small heat loss, so an all-electric ICF house with a heat pump, an electric boiler for backup, induction and an EV still usually fits on 200 A when it is planned. The same house in leaky frame with baseboard heat often does not. Our ICFhome.ca showhome in Tiny Township heats on radiant floors for about $100 a month in the coldest part of winter.
Questions people ask
Can you run electrical wire in ICF walls?
Yes. The cable runs in a channel cut into the inside foam with a hot knife or router, at the depth the code requires, and is protected where needed. The boxes are fastened to the plastic or steel webs moulded into the forms.
Does wiring an ICF house cost more?
Not much, if the electrician has done a few. No Ontario contractor we found publishes an ICF premium. The expensive mistake is a forgotten sleeve, which becomes a core drill at $150 to $400 a hole with the patch, our allowance.
How do you add an outlet to an ICF wall later?
On the inside face it is an ordinary job for an electrician: open the drywall, cut a channel in the foam, set the box on a web, patch. Going through the wall to the outside is the hard one, because that means drilling the concrete. Plan those before the pour.
What has to be sleeved before the pour?
The service entrance, the heat pump line set and feed, every exterior light and receptacle, hose bibs, dryer and hood vents, HRV hoods, a generator inlet, any EV feed to a detached spot, and low voltage to the outside. Add a spare or two.
Will an all-electric ICF house fit on 200 A?
Usually, when it is planned, because the heat loss is small. The load arithmetic is in the service capacity calculator.
Price the wiring, then check the list
The whole-house electrical cost calculator prices an ICF house the same way as any other, with the add-ons you choose. If you have an electrical quote for an ICF build, the $99 review reads it, up to three quotes, and tells you whether the penetrations and exterior work are in it.
Sources and further reading
- Ontario Electrical Safety Code: ESA on the 2024 (29th) edition in force since May 1, 2025, and what changed for houses, EV loads and energy storage.
- ICFhome.ca: where I build the ICF houses these wiring and electrification notes come from.
- ICFPro.ca: ICF walls and foundations, including planning the sleeves and penetrations before the pour.
