Electrical cables and downlights in an insulated loft

Cables

Electrical cables give off a little heat when they carry current. Out in the open, that heat escapes; buried in thick insulation, it can’t, and the cable runs warmer. For lighting circuits this is rarely a problem, but cables for showers, cookers and other heavy loads are sized on the assumption that they can lose heat. Where possible, we lift cables so they sit on top of the insulation, or clip them to the side of a timber above it. If a heavy-load cable has to run through insulation, an electrician should check it is suitable.

Old cables, especially rubber- or fabric-covered ones from before the 1960s, shouldn’t be buried at all. If you see them, mention it: an electrician should look at them first.

Downlights

Recessed downlights cut a hole through the ceiling into the loft. Older halogen downlights run hot and need space around them; covering them with insulation is a fire risk. LED downlights run much cooler, but the fittings still need to suit being covered. Options include:

• Downlight covers or hoods placed over each light in the loft, so the insulation can be laid around and over them
• IC-rated fittings, which are designed to be covered by insulation
• Keeping a clear gap around the fitting, which leaves a cold spot but is safe

Fire-rated or sealed covers also stop warm, moist air leaking up through the holes, which helps with condensation.

Junction boxes

Leave junction boxes accessible and visible. Burying them in insulation makes them hard to find when something needs fixing.