No, that's not common in this area at all– Local contruction is primarlily thick limestone walls, with lime mortar. Breathable and well insulated on its own. Walls are 40cm thick and provide fairly decent insulating properties – Takes time to warm up in winter, but once warm stone holds heat a long time. Especially good for keeping heat *out* in summer, with no need for A/C! Some people do use insulation bewteen stone walls and interior drywall, or you can opt for something more eco-friendly (and breathable which the walls will appreciate!) by using cob, mixed with straw, wool, or similar materials on the interior walls. Biggest insulating bump would be from replacing the existing original windows on lower level since they are single pane and quite out-dated.