Loft insulation - preventing condensation?

NewtoDIY

I need to install loft insulation and have been reading about the various problems with potential condensation. The loft is currently cleared and the eaves are well ventilated. The roofing felt looks to be in good condition with no noticable breaks. The only thing I cannot see is how the roof can breath at the top of the ridge because it looks like the felt totally seals the apex. If I lay insulation to say 300mm, and hot air permeates through this somehow, where is the ventilation travelling?

It's a Victorian house with joists spaced at 32cm and 60mm deep and I want to lay it as a cold roof.

Any thoughts or suggestions would be appreciated

http://i1275.photobucket.com/albums/y443/diyuserneedshelp2013/20130911_150628-Copy_zps05fc7944.jpg

http://i1275.photobucket.com/albums/y443/diyuserneedshelp2013/20130911_150649-Copy_zps83aa72f7.jpg

sk240

The air will pass from one side of the house to the other, so shouldnt be a problem

NewtoDIY

Thanks for that!