Loft Insulation, wiring air gap, cable tray/basket

25 Sep 2022
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United Kingdom

Insulating loft and the existing cabling is clipped to loft boarding, being a cautious type I'd like to avoid any risks. Is putting a steel cable basket or cable tray upside down over the cables to leave a 25mm air gap between the wiring and insulation ok? Would be using 150mm Rockwool on top of existing insulation between the joists. (So bottom to top would be ceiling, 100mm rockwool, 20mm loft board, cables, 25mm air gap under cable tray, 150mm rockwool.)
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I think the idea is the heat will transfer to the beam or plaster board to which the cable it attached or lying on, in the main being in contact with some thing will cool it better than being in free air, but we talk about free air, not air contained within a limited area.

However with maybe the exception of a shower feed cable, cables in the loft don't carry much current, in the main the ceiling rose is rated 6 amp and is used as a junction box, so lighting supplies in the main limited to 6 amp, Method 103# (in a stud wall with thermal insulation with cable not touching the inner wall surface) with 1 mm² cable it is rated at 8 amp, table 4D5 so in the main not a problem.

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