Cold roof deck ventilation - necessary?

15 Oct 2014
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United Kingdom
I have seen notes on a cold roof system on the web link (see below )I notice that it mentioned that sometimes cold roofs need ventilation and I wondered it if is possible to not have ventilation?:

We are planning a cold roof deck above a bedroom which will form a roof terrace.

Due to space constraints, it is currently designed as a cold roof construction -

The design comprises terrace tiles on spacers on EPDM single ply membrane on WBP ply on timber firrings laid to fall on 150mm Rockwool insulation within 150mm timber roof joists, vapour barrier above ceiling boards.

Can we do a similar cold roof construction without ventilation requirement or as we will have firrings for the flat roof drainage, should this be utilised as a ventilation zone? Due to a perimeter barrier issues the current design has a gable end balustrade channel detail that makes side ventilation difficult to achieve. Basically, ventilation will be difficult as there will be a fixed continuous balustrade channel for a glass balustrade all round the external edge of the roof terrace.

I wondered if we used celotex/kingspan between the joists and siliconed and taped the joins in the celotex and used insulated plasterboard on the ceiling with a full vapour barrier above it, whether this would be acceptable and would avoid the need for ventilation?

I hope someone can help! Thanks in advance! :)
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