Oh dear, cavity wiring and new insulation.

[Adam_151]

2) As an installer you should know that putting insulation over the cables could cause a fire. If you don't you are incompetent and should be fined/jailed if you carry on installing.
.

Playing devil's now...

How likely is it that an overloaded cable will cause a fire, I'd speculate that loose connections/underrated terminals would cause far more, and while I accept that overloaded cables close to terminals can heat the terminals and degrade the connections, perhaps if we take a second to consider just cables alone:

if you take the example of the contractors who upgrade glass fibre insulation in lofts to 270mm under many grant schemes available... the installation method from what I have seen is to just chuck it in, burying cables and all... whats the true risk of starting a fire, putting aside the fact that a lot of circuits in houses are underloaded for the time being, then considering the cable is pvc/pvc which goes soft at ~120 degrees C, and glass fibre isn't renowed for being easy to set on fire!... then I'd perhaps expect the likely outcome is for the conductors to migrate through the PVC and touch one another on a bend, resulting in a a bit of a bang and a blown fuse-link, rather than a fire

None of which excuses sloppy work of course, but perhaps explains why the accident statistics are low

 

[ban-all-sheds]

I agree entirely with your sentiments, but as there doesn't seem to be a practicable way of telling that there is cavity wiring then the conclusion must be that (foam) cavity wall insulation should be banned as a trade.

If there really isn't a way then maybe it should be banned.

I asked as I don't really like to hear workmen, who may well be perfectly competent, called cowboys.

If they do something without checking if a side-effect might be to burn the house down I struggle to regard them as averagely competent, let alone perfectly so....

 

[ban-all-sheds]

if you take the example of the contractors who upgrade glass fibre insulation in lofts to 270mm under many grant schemes available... the installation method from what I have seen is to just chuck it in, burying cables and all...

Incompetent and negligent. (And I can't be bothered to check, but I'd not be surprised if it contravened the Building Regulations, and was therefore illegal).

None of which excuses sloppy work of course, but perhaps explains why the accident statistics are low

That, and the fact that most cables in lofts are lighting circuits, which typically have a lot of headroom...