Insulation, Radiant and Vapor Barriers - ventilation between roof decking and insulation

Greetings,

I am going to sheetrock the inside of my walk-up attic. Up to now, the 50 year old insulation nailed up to the rafters of my 75 year old house has had decent ventilation behind it because it sags a little. I presume the ventilation will be stopped up when I compress the insulation behind the sheetrock.

What can I do to keep air flowing behind this insulation from soffit vents all the way to the ridge vent?

Also, I have two skylights completely blocking the bays. What could I do to improve the ventilation above and below them?

J

Styrofoam baffles applies under the roof decking first then the insulation then the insulation. The skylights do pose a problem with adequate ventilation but the baffles reduce the probability of a problem occurring.

Thanks for your reply! I'll ask for styrofoam baffles when I go to the store tonight.

I notice some small space around the skylights, so perhaps I can use styrofoam pieces and leave an airgap on either side, to allow some airflow.

This might create a cold short-circuit, but on the other hand, it will allow for air flow and keep the weakest part of the roof from failing down the road.

Am I right in this line of reasoning?

J