Insulation and cables

[Michaelsf90]

I'm in the process of overboarding a lathe and plaster ceiling. Battens on the ceiling and then fireline plasterboard. In the gap between the ceilings I was planning on putting some acoustic insulation in the space between the fireline board and the lathe and plaster ceiling. The cables are obviously above the lathe and plaster ceiling in the void between the floors. This will be insulation free so the only cables I need to be careful with are the ones coming through to the lights in the rooms where the ceiling is being boarded. This sounds correct doesn't it?

 

[JohnW2]

I'm in the process of overboarding a lathe and plaster ceiling. Battens on the ceiling and then fireline plasterboard. In the gap between the ceilings I was planning on putting some acoustic insulation in the space between the fireline board and the lathe and plaster ceiling. The cables are obviously above the lathe and plaster ceiling in the void between the floors. This will be insulation free so the only cables I need to be careful with are the ones coming through to the lights in the rooms where the ceiling is being boarded. This sounds correct doesn't it?

It certainly sounds right to me ... and I personally wouldn't worry about the very short bit (presumably only an inch or three) of cable going through the insulation to ceiling lights.

In fact, the cables we use for lighting circuits are so 'over-specified' that, even if they were much more intimately associated with thermal insulation, such that they has to be 'de-rated' because of that, they'd still probably be OK.

Kind Regards, John

 

[Michaelsf90]

Thank you John. The gap between the new plasterboard ceiling and the lathe and plaster ceiling will be full with acoustic insulation. The void between the lathe and plaster and the floorboards for the first floor will be completely insulation free. I thought it would be ok as their is plenty of room for the heat to dissipate. I think it's only wired in 1mm twin and earth although it's all leds so the load will be minimal

 

[JohnW2]

Thank you John. The gap between the new plasterboard ceiling and the lathe and plaster ceiling will be full with acoustic insulation. The void between the lathe and plaster and the floorboards for the first floor will be completely insulation free. I thought it would be ok as their is plenty of room for the heat to dissipate.

Indeed - and, as I said, I would personally not regard the very small length of cable going through that insulation (as I said, I presume probably only an inch or two) as being of any consequence.

I think it's only wired in 1mm twin and earth although it's all leds so the load will be minimal

As I implied, even 1 mm² T+E is 'over-specified'. Your 1 mm² T+E above the lath and plaster has a current-carrying-capacity of 16 A. Even if it were totally buried in thermal insulation, that would only reduce to 8 A - hence fine for a 6A lighting circuit (even if it were 'fully loaded').

Kind Regards, John

 

[Michaelsf90]

Thanks a lot John