Wall insulation - why is it better from the outside, not from the inside?

Proper insulation of a building requires taking into account two physical phenomena - energy transport, i.e. heat, and water vapor diffusion in sandwich partitions. Insulating the walls from the inside causes the wall freezing zone, and thus also the water vapor condensation zone, to shift towards the inside, which may cause the partition to become damp and reduce its durability.

With traditional insulation, these phenomena do not occur from the outside. The wall is always located in the warm zone (outside the frost zone) and, importantly, it heats up with the room. It has the same temperature as the air inside.

It stabilises the operation of the heating system due to its high thermal inertia and has a positive effect on the interior microclimate and thermal comfort due to the humidity capacity. There is no condensation of water vapor in the wall and there are no large differences in temperature between summer and winter, which ensures the stability of the structure. Therefore, whenever possible, it is recommended to lay insulation on the outer side of the wall.