light fitting through ceiling insulation/ vapour barrier?

[howdood]

Hi - just getting ready to insulate a section of concrete ceiling in my flat, where there is a lot of heat loss as it's below the walkway access to the flat above. I'm planning to use battens + insulation + foil-backed plasterboard... only problem is that there is a light fitting so I'll need to bring wiring through the vapour barrier to refit the light on the new ceiling.

I'm worried about compromising the vapour barrier and having moist air get through where I bring the wiring down - is there a standard way of preventing this?

Thanks!
h

 

[PrenticeBoyofDerry]

It will not be a big issue and should not compromise what you have in place.
If you really wanted to, you could seal the hole from where the cables will drop, using a sealant such as silicone.

 

[^woody^]

It's a flat not a submarine, you don't have to worry too much about sealing everything up