Cold roof with no VCL? With spotlights?

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Hi All,
Wonder if anyone can shed some light on this. I'm no builder so please bare with me. We've had a single storey pitched roof extension built with a vaulted ceiling. The roof construction as done by our builder, is a cold roof as follows:

Slate Rood
Breathable Membrane
200mm rafters with ventilation gap and 100mm Celotex inbetween (celotex below ventilation)
plasterboard backed with 40mm Celotex

I have sketched a profile - hope it all makes sense.
They have got as far as fitting the Celotex between the joists and following a conversation with the building control officer I have some concerns - I'd appreciate some advice.

1. Do we need a VCL? The 100mm Celotex has a foil layer, as it looks like the plasterboard insulation does on either side of the insulation, but there has been no taping of joins and no plans to add a VCL. Is this ok?
2. We are having spotlights in the ceiling - the builder planned to leave gaps in the 100mm Celotex for them, but as building control has pointed out this means there are cold spots in the roof and the light is exposed to the vantilation gap and will get condensation on and rust. He advised cutting out halfway through the celotex to leave a space for the light but also 50mm of insulation above it. However this would mean cutting through the foil layer. Is this ok?

From the research I've done it appears that neither is acceptable. Is there any way we can add a VCL and still have spotlights in the ceiling? I know we could have surface mounted but I'm trying to avoid that.
Thanks very much for the help!
Matt
 

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Change your lighting, there are large downlights available now, that are the thickness of plasterboard! As long as you can find somewhere for the driver, then it means it can sit below the insulation, so no issue.
 
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+1 for change lighting... I wouldn't cut the insulation.

If you do decide to cut a pocket halfway through, you can line it with foil tape to carry on the foil layer, but there won't be any noticeable gain.
 
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+ another for different lighting!
If you feel brave, have a search on the electrical forum for spotlights and see the vitriol! ;)

I have a couple of these and they are very good:
They are flush fitting with a built in driver - however, if they fail, the whole unit will need replacing.

Other systems, such as cable lighting can look good in a vaulted space, but do need regular dusting! :)
 

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