Why it is impossible to insulate aerated concrete and brick houses with EPS: we understand the issue

In social networks and Internet forums, disputes on the topic: “Is it possible to insulate walls from aerated concrete, brick and expanded clay concrete? extruded polystyrene foam? " As always, one part stands for, and the other believes that, firstly, a stone house should not need insulation outside; and secondly, if you choose a heater, then only not EPS. Let's try to understand the question.

The point is vapor permeability

Extruded polystyrene foam has a very low vapor permeability coefficient (depending on density - 0.05-0.005 m / h / Pa). This means that he is very bad at letting go of steam. And at a stone wall, be it aerated concrete, expanded clay concrete or ceramic brick, vapor permeability is several times higher. This means that all the moisture in the house will not go outside, but will accumulate in the wall material, since the EPS prevents it from escaping. That is, the extruded polystyrene foam becomes a vapor escape barrier.

For such walls, it is wiser to use stone wool, the vapor permeability of which is close to the vapor permeability of wood. In this case, all moisture-saturated vapors will be discharged from the wall through the insulation. In general, in the correct "pie" of a stone wall, vapor permeability should increase from the inside out. A minimum of steam should get into the wall material, and the one that gets there should come out without any obstacles.

Aerated concrete wall with a vapor permeability of 0.20 m / h / Pa should be insulated with a heat insulator with a higher vapor permeability. As, for example, stone wool, the vapor permeability of which is 0.30 m / h / Pa. In this case, steam will not accumulate and condense in the wall. And if you apply the above EPS, then the moisture will not have time to come out in the amount in which it comes. And this will lead to its inevitable accumulation in the wall and, accordingly, wetting of the wall material.

In what cases can stone houses be insulated with EPS?

EPPS can be used in cases where the house is completely (not only the kitchen and the bathroom) is equipped with a forced supply and exhaust ventilation system and it works all year round. With such a ventilation system, all moisture-saturated vapors will be removed. But not everyone can afford such a system. Now 9 out of 10 houses do not have such ventilation; the maximum that is installed is a duct fan in the bathrooms and in the kitchen. But for a problem-free insulation of stone houses with EPS, this is not enough.

How did you insulate your house? Write down the material used, its advantages and disadvantages.

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