Russell writes: "Is it necessary to install insulation stops between each and every rafter for attic ventilation or can you go, say, every third space?"

Answer: Keep in mind that the more vents at the soffits, the more ventilation you will achieve, which is a good thing. More ventilation will help result in a longer life for your roof. You may want to check updated code requirements in your area for ventilation requirements. Minimum ventilation is one square foot of ventilation for every 300 square feet of attic space (1/300). Owens Corning recommends a 1/150 ratio.