When I renovated my house (temperate EU climate), this was actually mandatory: active ventilation and breathing vapor shield in front of the insulation layer.

Indeed, older houses rely on "gravity ventilation", as my architect described it: high-temp heating is used to move stale air around by induction, plenty of nooks and crannies together with the density gradient would suck in fresh air.

When you renovate partially, adding insulation layers and plugging holes, you need to open up the windows for about 5-10 minutes once or twice a day. Paradoxically, the heat loss is mitigated because the fresh air is typically drier, which heats up easier.