Okay, let's break down the wiring requirements for fans and lights under a pérgola (spelling correction) roof, assuming it's insulated with Styrofoam and waterproofed.

Key Considerations


Location

Even with a waterproofed roof, a pérgola is generally considered a damp or wet location. This is because humidity, condensation, and potential rain splatter can still occur. It may not be directly exposed to the weather.2.

Wiring Method

Since the pérgola is insulated with Styrofoam, you are working in an inaccessible area once you close up the ceiling.3.

Wiring Codes

Electrical codes (like the NEC in the US) are very specific about wiring in damp/wet locations.

Approved Wire Types (Generally)

Considering the above factors, here's a rundown of suitable wire types:

UF Cable (Underground Feeder)

This is a very common and safe choice for wet and damp locations. It's designed to be buried directly in the ground, so it's inherently resistant to moisture. The conductors are embedded in a solid plastic (thermoplastic) jacket. Overkill? It might seem like it, but UF cable gives you a very high degree of protection against moisture and physical damage. It may be the simplest and cheapest option to buy.

THWN/THHN Conductors in Conduit

THWN and THHN are individual insulated conductors approved for wet locations when installed in conduit. Conduit provides a protective raceway for the wires, shielding them from physical damage and moisture. Options include rigid metal conduit (RMC), intermediate metal conduit (IMC), electrical metallic tubing (EMT), or rigid PVC conduit (schedule 80 PVC is usually recommended for outdoor/exposed locations). This can be a good option if you want a more robust installation and need to protect the wiring from physical damage (e.g., from tools, tree branches, etc.). Important: All conduit fittings must be watertight.

MC Cable (Metal Clad Cable)

MC cable with a grounded metal sheath can be used in some situations, but only if it is rated for wet locations. Check the cable's markings to be sure (it will state "suitable for wet locations," or similar). This is typically more expensive than UF.

Why Romex (NM Cable) is NOT Approved



Romex (NM Cable): Absolutely do NOT use Romex (NM cable). This is standard indoor wiring and is not rated for damp or wet locations. It will corrode and can become a serious safety hazard (shock and fire risk).

Important Considerations for Installation



Proper Boxes

Use weatherproof electrical boxes (rated for outdoor use). These boxes have gaskets and seals to keep moisture out.

Watertight Fittings

Use watertight connectors and fittings for all conduit and cable connections.

Drip Loops

When wiring to fixtures, create a drip loop in the wire. This helps prevent water from running down the wire and into the fixture or box.

Grounding

Ensure proper grounding of all metal boxes, fixtures, and equipment.

Local Codes and Inspections

This is critical. Electrical codes vary by location. Always check with your local building department or a qualified electrician to determine the specific requirements in your area. They will be able to tell you what is allowed and what permits are needed. An inspection is usually required to ensure the work is done safely and correctly.

In Summary

While UF cable might seem a bit overkill, it provides excellent protection against moisture, which is vital in a pérgola* setting. THWN/THHN in conduit is also a good choice for added protection.

Never use Romex (NM cable) in this situation. Always consult with a qualified electrician and follow local electrical codes to ensure a safe and compliant installation. Flag for review