Insulation between rafters

In this attic the insulation has been placed between the rafters, instead of in the floor between the joists or on the knee walls. This method of installation can result in mold forming of the substraight and in cases where plywood is used delaminating due to the moisture trapped. Only in newer homes properly designed for this type of system can it be installed. In these cases a minimum of a 2" x 8" rafter is used for R 19 (6") of insulation with continuous ridge and soffit vents installed. This allows for air movement in the 2"± space between the insulation and the substraight.