Aerated gap influence on thermophysical characteristics of external heat insulation of building fasades with using of thin-coat plasters

Recently the systems of external warming of building facades with application of thin-coat plasters become more and more popular. The primary goal for manufacturers of dry mixes is improvement of thermotechnical characteristics of a protectively-decorative layer, especially regarding its vapor permeabilty. For today the average index of vapor permeabilty for many glutinous and plaster structures makes 0,01-0,03 mg/mchpa. It often yields negative result under the calculation of humidity conditions of the sctructure, namely: substantial increase of sorption humidity of a protectively-decorative layer is observed, and partial moisture accumulation in the annual period occurs. Under current quality of building, and also under possible critical combination of the specified conditions, the probability of occurrence of defects and decrease in durability of system grows.

Because of the big difference in temperatures of external and internal air during the winter period the considerable gradient of partial pressure of water vapour appears. Regular influence of specified negative factors can in time lead to partial destruction of the facade and decrease in heat-insulating properties of the external wall.

From recent time all problems set forth above are offered for solving by introduction in system of a special material – the facade mat providing a continuous ventilated layer under the plaster layer. Such decision should raise reliability and power efficiency of a design as a whole at the expense of deducing in environment of moisture arriving in a structure.

The article considers the influence of the ventilated layer on moisture condensation within external wall structure as an example of comparative field tests of external insulation composite systems.