insulation above flat roof on 1930s house

[essex123456]

I have a draft from above a bay window, its an upper floor bay with a flat felt roof. I have striped the lath and plaster to reveal the wood. Can I just fill this with rock wool? or do I need ventilation ?

I have looked on here but the posts I have found are for bays with tiles or ground floor with another bay above.

Thanks

 

[Alastairreid]

Better with rigid insulation, full filled hard against the deck...tape the joins with foil tape and install a vapour barrier...need to stop moisture from the room getting to the underside of the cold deck.
Proper way is insulation on top of decking...warm roof.

 

[essex123456]

Better with rigid insulation, full filled hard against the deck...tape the joins with foil tape and install a vapour barrier...need to stop moisture from the room getting to the underside of the cold deck.
Proper way is insulation on top of decking...warm roof.

Thanks for the reply, would I be best half filling with rigid insulation to leave ventelation at the top like a cold roof construction? Just done a 29sqm warm roof on our extension my brains frazzled not sure why I hadn't thought of it being like a cold roof construction.

 

[Alastairreid]

That would only work if you had ventilation in the gap you left, ie eave and wall abutment.

 

[essex123456]

Thanks for your help.