Cables embedded in thermal insulation - problems?

[Bosi]

I've noticed that BS7671 allow cables to be installed in thermal insulation, even if it discourages from it.
It even has figures of the derating factor in 523.7.

In Sweden, where I live, the regulations does not allow this. Well, it does not specifically forbid cables in thermal insulation, but it does not give any help to calculate the current-carrying capacity. The problem with this has been debated now and then, if it is a problem to bury the cables "just a little"...taking into account the normal use of the radial (the "design current").

Now, my questions:
Is this common practice in the UK?
Do you have any (bad) experience?
Does the reduction factors in 523.7 work well?

 

[kingeri]

Hi. We would generally avoid running any cables through thermal insulation whenever possible. If it is absolutely unavoidable, we would keep the length that passes through as short as possible. At the end of the day, the only bad experience is having to potentially use a larger conductor or compromise by reducing the fuse or circuit breaker rating.

 

[Guitarist]

I think that a 50% reduction in ccc is quite a good deterrent. Unfortunately, as with all things, many people simply ignore it.