RAFTER RAISE?

MY PROBLEM IN THE COOLER MONTHS I HAVE RAFTER RAISE
SEPERATION OF CEILING FROM WALLS. MY RELATOR EXPLAINED THIS TO ME. WHAT AND HOW IS THE BEST WAY TO OVER COME THIS BESIDE PUTTING MOLDING UP THATS
ATTACHED TO THE CEILNG AND ALLOWED TO FREELY MOVE UP THE WALL WHEN THIS OCCURRS,