A pro would use the baffles at every rafter space then insulate fully to the baffle. As said above, do not decrease ventilation into your attic space. In fact, make sure you have soffit vents at regular intervals of not less than 4'. Then make sure there are vents up high towards the ridge, or at the ridge, at very regular intervals. The ventilation helps move excessive heat out in the summer that can overheat the house and causes shingles to wear out more quickly. In the winter ventilation removes damaging moisture that will cause your rafters and roof sheathing to rot.
Proper thickness of insulation is important. You should have at least 12-16" of insulation in your attic depending upon the insulation type. At 12-16" of properly installed insulation there is almost no heat transfer so adding more insulation is a waste.
Last edited by jdougn; 02-20-2009 at 07:48 AM.