Dormer insulation

[DiyLady]

Currently upstairs is completely open I.e. I can see the felt in the roof (And can feel the breeze coming through it). We have spray foam from wall plate to purline and metac on the slopes up to the ceiling and nothing beyond. We don't have an airtight house so what would you advise to keep the cold air out? Would loftwool be enough above the ceiling? Should I use airtight membrane for the sole purpose of keeping the cold out? Also can anyone advise where to buy insulation that doesn't cost the earth.
Thanks in advance!

 

[Micks'r]

Your post isn't clear to me!

If you have spray foamed from the wall plate to the purlin and above this is the metac, where are you seeing the roofing felt?
Perhaps you might sketch out what you have or even take a few photos.

That breeze you are feeling is likely the ventilation of the roof and is very important to keep your roof timbers dry.
It seems to me your conflating this ventilation with air tightness of the house and the insulation may well be in the wrong place. I see this a lot where the insulation envelope follows the roof rafter line from the wallplate to ridge whereas it ought to follow the groundfloor ceiling, 1st floor knee wall, sloped ceiling and across the flat ceiling. Then the airtight barrier is on the warm side of this. Defining this thermal envelope is crucial to making the correct choices going forward.

I may well have completely mis-interpreted your post but some good sketches or photos would help a lot.