Loft Insulation and Electrical Wiring

[KateMoss]

Hi, I am about to install loft insulation (mineral wool - SPACE 'Loft Roll') and the instructions on the packing say 'Insulation must not be laid over electric cables'.
This implies I need to lift the lighting cables which are currently (ha ha !) fixed to the joists so that they end up above the finished level of the insulation. (They would be buried by about 200 mm if left as they are).
I asked a pro who came to give an estimate if his company would raise the wiring and he said 'No'.
I'm sure the instructions are good advice but it seems a bit over the top to me; do I run a serious risk by not following them? Thanks.

 

[regsmyth]

Well yes there is a risk. This is covered from time to time in the electrics section - do a search.
They should lift all the cables, but they won't. Brilliant.

 

[Daka]

Generally the rule is that you lay wiring on top of the insulation to allow air to cool warmer cables down. In my view this is not a big risk but it is a good idea to do.

What you can do is make sure there is a gap around the cables by putting them in channelling. You can get stuff that you can right over the top of the fixed cables.

This will give extra mechanical protection & allow air to move freely around the cables.

The profile looks a bit like this:

_/‾‾‾\_

You can get it from most DIY places. This is some from screwfix but you can get different sizes:
http://www.screwfix.com/cats/A331823/Electrical-Supplies/Conduit/PVC-Channel

 

[KateMoss]

Thanks regsmyth and Daka, I have had some useful replies from 'electrical' as you said reg and your advice re. profiles is also v.useful Daka.

 

[mointainwalker]

You run next to no risk from lighting-wiring , logically the most common up there.

Significant problems could arise if you had major power-users such as :

1) Electric-shower
2) Immersion-heater

attached to the joists.

Since sparkies don't leave metres of spare cable lying around, the bit about not putting cables under insulation is just a legal get-out. slap-in-the-face for the owner.