roof vent + celotex insulation

[mazears]

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I have a pitched roof over the kitchen area which i've had to board out and felt over(due to low angle). I have yet to fit the tiles. There is no soffit, as joists end up nearly flush (or will be once rendered) with wall. I was then going to put pvcu fascia on the end joists then gutter it...I presume i need to vent the area beneath the boards to stop condensation/rot. In this situation what is my best option-to use Timloc vents as shown or can i just drill few holes through the fascia/wood noggins into the roof void? There is an inch or two gap directly above the concrete lintel-maybe i can use this to ventilate under roof boarding? Also there seems to be no way of venting the roof sides or is this unneccessary as will be rendered over?
Each joist is 150mm deep. I have bought 70mm celotex to insulate from inside. Do i fit flush with joist edge then fit plasterboard flush on top of this or will this leave no room for electrics/ceiling lights? Is it best to use vapour sheeting under the finished plasterboard? Thanks for any questions answered!

 

[justlead1]

Hi. If you intend to ventilate at eaves you will need to ventilate at head of roof at brickwork abutment. Otherwise air will not circulate.

 

[mazears]

Can i get away with not venting at all as both eaves and ridge top are sealed. Read another post that said you can completely fill between underside of rafters (150mm deep) + expanding foam sealing edges + vapour check + plasterboard. Will this work or is there a more simple solution? I've already bought 70mm celotex will this suffice?

 

[justlead1]

Hi. Have a google of hot roof cold roof this will give you some options.

 

[mazears]

Hi. Have a google of hot roof cold roof this will give you some options.

not too sure what this involves

 

[justlead1]

Hi.
http://www.countyflatroofing.co.uk/insulation.html There is a pictorial explanation that may well address your roof requirements.

 

[mazears]

The boarded roof is already felted and counterbattened so have only the thickness of the counterbatten if i was to put insulation above the roof. If i carry on with the cold roof scenario and not vent anywhere do i have to completely fill the depth of the rafters internally ie.150mm with insulation to prevent future condensation, especially as this is the kitchen area?

 

[mazears]

I've decided to use an over fascia vent as in bottom middle pic. The gap at head of roof joining against main wall is only about 1inch..(1)-Will this be sufficient to let airflow out, and is the gap simply left as a gap or is there some type of special vent slotted in here also? Also, i originally had wooden noggins supporting each ply boards edging (where one board met the next-you can see in pic) as i put ply boards on across ways(wrongly i think) to the rafters. I.ve just knocked these off as they are going to be in the way of the 50mm air gap/insulation. (2)-Do i need to seal this internal join with anything? After banging noggins off slight damp patches/mold spotting was visible,this being after only about 4weeks. Ice patches were there too although i think because of the nails i originally knocked into noggins from above. I was thinking of sealing each join with wider pvcu strips/silicone or is it best to leave for air to get to. (3)-I.ve sealed the underside of ply with sbr bonding, is this good enough. (4)-is a 30mm gap between insulation and plasterboard sufficient for fitting spot lights that sit within the plasterboard or can i get away with less than that? (5)-Before putting tiles back on, am i best also using normal roofing underlay between the counterbattens and cross battens or is the already ply and felted board sufficient enough? ...Thanks