Probabilistic assessment of failure risk of the building envelope thermally insulated from the inside

Thermal insulation of external walls is designed in particular to reduce energy performance of buildings. Insulation placed on the outer side of walls act as an effective protection against the external environment. On the contrary placing the thermal insulation layer on the inner side of the building envelope is quite hazardous as the internal insulation does not fulfil the protective function. It actually exposes the bearing layer of the building envelope to the immediate effect of the environment and therefore it enhances the negative impacts of the cyclic temperature changes on structural system of the building. This paper focuses on probability risk of development of failures on such construction depending on variable boundary conditions (rigidity of the structure, strength of the materials, and range of the temperature load). Besides this there is also comparison of probability and deterministic approach to the evaluation of static reliability of the building constructions. Using of probabilistic approach in this context is still very rare. The aim of this paper is to analyse the effects of internal insulation on load bearing system of buildings, and to verify the applicability of probabilistic methods in the analysis of structural reliability. Like the deterministic approach, it draws attention to the high risk of failure of the structures insulated from the inside. At the same time, however, it shows the high demands of the probabilistic method on the amount of input data. If the data are not available, it is possible to replace some of them results of deterministic method; this approach has negative consequences in mutual dependency of accuracy of achieved results.