Mike writes from Methuen, Massachusetts: "I want to insulate my attic rafters and I have a soffit and rige vent vent system. Are the pink foam rafter vents adequate ventilation and what r value insulation can I use with 2x10 roof rafters?"

Answer: The Raft-R-Mate® attic rafter vent system is used to maintain ventilation between the soffit and the ridge of the roof. Check to make sure this ventilation is not blocked at the eave or ridge, and that there is an equal amount of ventilation in the soffit as there is in the ridge of the roof.

There is information on the Owens Corning website that will help you determine the amount of ventilation you need. You will need to do some math to calculate your ventilation requirement. The minimum ratio is 1/300. That means you need one square foot of ventilation for every 300 square feet of attic space. We recommend a ratio of 1/150.

Regarding the insulation, are you asking about the rafters on the sloped part of your roof or the floor joists? If you have an unfinished, unconditioned and well-ventilated attic, you should insulate the floor joists and not the roof. For your area, the U.S. Department of Energy recommends R-49, which is about 15-1/2 inches of fiberglass insulation. You should first fill the floor joist cavity with insulation, then place additional unfaced insulation on top perpendicular to the first layer.

If the attic is to be finished, we recommend R-30C in the roof rafters.