Cable routes through insulation

[Mike2007]

If a very thick amount of fibre glass insulation is to applied to a loft space. How can lighting cable be run to its terminations without serious de-rating of the lighting cable?
1.5 csa t&e flat thermoplastic cable
No long runs (over 10m)

Thanks

 

[flameport]

Not normally a problem even with 1mm. With insulation on all sides, it is still rated to 8A. Most lighting circuits will have a 6A breaker.
If the cable is touching the ceiling surface, the rating is higher.