Drywall cracks

[vabuilder]

In the summer of 2009 we completed a renovation of an attic into living space. The drywall ceiling is attached to the original roof rafters and to rafter ties that were installed at 8 foot above floor level. Every winter serious cracks show up in some areas at drywall joints. It always happens at the same locations. We have repaired the cracks but they always re-appear the next winter. The insulation between rafters is closed cell foam. I am not sure how to permanently repair the problem.

[MarkMc]

research truss lift.