To Insulate Kitchen Flat Roof or Not That is the Question

[diyfish]

Hi DIY Gurus,

I've stripped my kitchen ceiling as part of renovation work and noticed that we have no insulation under our flat roof.

I would like to fit insulation using the cold roof method but building regulation states that it can cause serious condensation issues if I don't have ventilation from opposite sides.

I only have one side ventilation and will be unable to create ventilation on the other side. Is it possible to insulate my roof or should I just give it up?
I thought to do the following but I am no expert and I don't know if the single side ventilation will create problems which I'll better avoid.

If it is possible can I do the following or is there a better way?

1. Fit 100 mm Kingpsan at the bottom of the Joist. (This will leave 50mm gap on top of the insulation).
2. Fit 2 layers of vapor barrier (1 layer from west to east and 1 layer from north to south)
3. Fit fire resistant plaster board.
4. Skim it all


Many thanks for your input!

[welsh brickie]

everything listed is fine, apart from the vapor barrier, you don't need it