Insulation around wiring

gun foam - shouldn't hurt the cable and a short insulated section makes no real difference.

If you are worried, stick a split bog roll or something around the cable and foam upto that, leaving a clear way for the cable.

But FTAOD do not allow a route for a draught of cold air to come up from under the floor behind the skirting board. At the very least plug the ends.

Use fire rated, the white stuff can go off like a firework

NT

Some times insulation derates the current carrying capacity of the cable.

You don't usually worry about 100mm or less if the cable passes through it.

If the insulation is covering the cable, that's different, but it doesn't sound like that's the case here?

I have just been working in a "super insulated" new build,

Super insulated my arse.

There was a draught at the back of every wall when I was fitting the sockets on the dry lined walls.

Some Building Control departments test a house (or a small samples) for leak rate. I guess these have never been checked?

Yes, the insulation could cover the wiring - but only the 50mm that runs down the wall.

I'll caulk the hole where the cable goes through the floor and fashion a length of conduit for that 50mm.

I've noticed that in my once uninsulated old build. Remove a socket or switch on a windy day and quite a gale blows through.

That house will be pressure tested. They will foam gun all those cracks.

I think that's only guaranteed if it's a stand-alone build. Last time I looked the regs only required an air permeability test on three units of a kind on an estate. And even if that test is done properly, by a truly independent contractor, I don't see a few squirts of foam behind sockets making good underlying problems such as missing vapour barriers.

AIUI if it's an estate, the builders only need to pressure test a small sample of the houses ... will they seal the others?

Or pay off the guy doing the pressure testing to give it a pass?

It happens.