Use Case
Running electrical wiring through EPS (Expanded Polystyrene) sandwich panels requires more than just a drill and a cable. Because cool rooms rely on an airtight seal to maintain temperature, every hole you drill introduces a potential "thermal bridge" or air leak. Furthermore, there is a critical chemical reaction between standard electrical cables and polystyrene that many installers overlook.
Whether you are installing lights, switches, or refrigeration units, follow this guide from the experts at Cool Room Master to run wires safely, maintain your insulation value, and comply with Australian safety standards.
Figure 1: Always protect your wiring. PVC cables can react chemically with EPS foam over time.
⚠️ CRITICAL WARNING: The "PVC vs. EPS" Reaction
Never let standard PVC electrical cables touch the EPS foam core directly. The plasticizers in PVC cables react chemically with polystyrene foam (migration). Over time, this causes the cable insulation to become brittle and crack, and the foam to degrade. You must always use a conduit to separate the wire from the foam core.
Never let standard PVC electrical cables touch the EPS foam core directly. The plasticizers in PVC cables react chemically with polystyrene foam (migration). Over time, this causes the cable insulation to become brittle and crack, and the foam to degrade. You must always use a conduit to separate the wire from the foam core.
Option 1: Surface Mounting (The Preferred Method)
For most cool rooms, surface mounting is the industry standard. It preserves the integrity of the panel insulation and makes future maintenance significantly easier.
- Preserves Insulation: No channels cut into the core means no loss of R-value.
- Vapour Barrier: Reduces the risk of moisture entering the panel.
- Ease of Access: Electricians can easily access wiring for repairs without cutting open walls.
Recommendation: Use UV-stabilized PVC conduit or dedicated cool room cable ducting mounted directly to the Colorbond skin of the panel. You can view our range of panel accessories and mounting channels by contacting our team.
Option 2: Internal Wiring (The Hidden Method)
If you require a flush finish (common in clean rooms or high-traffic areas), you can run wires internally, but it requires precision.
Internal wiring must always be housed in a rigid conduit to prevent chemical reactions.
Step 1: Create a Clean Pathway
Unlike stud walls, you cannot "fish" a wire easily through solid foam. You will usually need to drill a channel. If the panel is already installed, this is difficult over long distances. It is best done during the panel assembly phase or by using a heated ball bearing method (for professionals) or long auger bits for short distances.
Step 2: Install Rigid Conduit
As mentioned in the warning above, insert a rigid PVC conduit into the hole you have drilled. This serves two purposes:
- It prevents the chemical reaction between the cable and the EPS core.
- It allows you to pull new cables through in the future if a wire fails.
Step 3: Seal the Penetrations (Crucial)
This is where most DIY installs fail. If warm air enters the conduit from the outside and meets the cold air inside the cool room, condensation will form inside your electrical fittings.
The Fix: Once the wire is pulled, seal both ends of the conduit with high-grade silicone or expanding fire-rated foam. This prevents airflow and stops ice buildup inside your light switches or junction boxes.
Safety Checklist for Cool Room Wiring
Before powering up, ensure your installation meets these checks:
- Penetrations Sealed: All entry and exit points are silicone-sealed to prevent moisture ingress.
- Conduit Used: No cables are in direct contact with the EPS core.
- Cold Bridge Managed: Ensure that metal conduits (if used) do not create a bridge for heat to transfer into the room. PVC is preferred for this reason.
- Waterproof Fittings: Inside the room, ensure all switches and lights are IP-rated (e.g., IP66) to withstand wash-downs and humidity.
Need Professional Advice?
Drilling into sandwich panels can compromise the structural integrity and insulation value of your cool room if done incorrectly. If you are unsure about the best route for your wiring, or need supplies for your project, Cool Room Master is here to help.