Can Insulation Touch Electrical Wires in the Attic?

Can Insulation Touch Electrical Wires in the Attic?

Loose-fill and batt insulation regularly come into contact with electrical cables in attics, and in most cases this is acceptable — NMD-90 cable is rated for use in insulated cavities. However, specific conditions require clearance and attention to avoid overheating or fire.

When Insulation and Wiring Are Compatible

• NMD-90 cable (the standard residential wiring used in Ontario) is rated for 90°C and can be in contact with thermal insulation
• Insulation blown or laid over cables running along joists is normal in most attics and does not require special treatment
• Cables stapled to the side of joists, fully embedded in blown insulation, remain within their rated conditions

When Clearance Is Required

• Recessed light fixtures (pot lights) that are not rated for insulation contact (not marked “IC”) must have a minimum clearance of 75mm (3 inches) from insulation — insulation packed against a non-IC fixture can cause the fixture to overheat and potentially ignite
• IC-rated fixtures are designed to be in contact with insulation and are marked “IC” — these need no clearance
• Junction boxes with open knockouts should not be buried in loose-fill insulation without ensuring the knockouts are sealed
• Knob-and-tube wiring (found in some older Ontario homes) must not be covered with insulation — the open-air cooling it relies on is blocked by insulation, causing dangerous overheating. If your home has knob-and-tube wiring, consult a licensed electrician before adding attic insulation

If you are adding attic insulation and are unsure what type of wiring or fixtures are present, EZSMART can inspect the attic, identify any incompatible conditions, and correct them before insulation is installed. Contact us for an assessment across Ontario.

Amir Azimipour

Electrician Since 2008 Journeyman Electrician Designated Master Electrician at EZSMART Corp