Stone walls are terrible for heat insolation. They have inertia but no insolation. So they are good in the Mediterranean coast where you want inertia in summer as some sort of natural climate control to keep it cool during the day. But they are terrible in winter when what you want is insolation to keep the heat in during months. A 1m stone wall doesn't even insolate as good than 5cm of dedicated insolation panels. It happens very frequently now that old houses are renovated by adding insolation to those old stone walls, but of course you lose the charm of stone on one side of the wall. This is why you have basically no stone houses in Scandinavia, because in winter it would just be impossible to heat.