[Greenbuilding] vented roofs

[Janet L. Hobbs]

 Hi Irina,

The current building science gurus seem to be the folks at eeba.org  I don't
know about your climate, but they are definitely advocating a non-vented
attic here in Central Texas.  I'm not completely convinced myself.  But,you
have started down that road due to the insulation choice you've made so you
should probably do the whole package deal, not part of it.  If you do
cathedralized insulation (insulating at rafters) you shouldn't vent the
attic because you are introducing (in our climate) hot, humid air into the
conditioned envelope of the house - which now includes the attic.  Any
ventilation should be outside that envelope.   Here, for instance, many
people still provide a little bit of an air channel between insulation and
shingles so that the shingles themselves are cooled off a bit.  I have heard
but not verified that some shingle manufacturers won't warranty their
product if it isn't ventilated.

EEBA has several publications that are specific to different climates. So,
you should see what they recommend for yours.  

Good luck with your installation.

-janet in Texas