Thermal Properties of Heat Insulating Materials under Quasi-Stationary Thermal Conditions

Maintenance of the best parameters of the indoor temperature is possible with properly selected heat insulation that provides both the required heat transfer resistance and thermal inertia indicators of building envelopes. This, in turn, reduces the energy consumption of buildings, energy costs and helps to protect the environment from additional harmful emissions.

Purpose: The aim of the work is to obtain actual thermal properties and compare them with the standard data in order to evaluate the real effectiveness of heat insulating materials for buildings.

Research findings: The properties of materials are determined in both steady-state and quasisteady-state thermal conditions using laboratory methods and theoretical studies. The analysis of the laboratory tests of the wall fragment shows a significant difference between the experimentally determined thermal conductivity coefficient and its theoretically calculated value. This difference is explained by inaccurate normative data used to convert the thermal conductivity coefficient from a dry state to the calculated value that accounts for the operational humidity. For basalt wool, the deviation is 44%, and for extruded polystyrene foam, it is 19 %. Theoretical calculations demonstrate good agreement with the experimental data obtained using the 2D calculation model and laboratory test results for basalt wool and extruded polystyrene foam under steady-state and quasi-steady-state thermal conditions. This agreement allows to successfully verify the developed theoretical model. The advantage of the theoretical approach is the ability to analyze not only 2D structures, but also more complex enclosing structures containing heatconducting inclusions.

Value: The analysis of the heat flow dynamics in the model of the outer building corner shows the advantages of using extruded polystyrene foam as thermal insulation. Under quasisteady-state thermal conditions, the structure with extruded polystyrene foam demonstrates more stable temperature indicators throughout its thickness compared to the similar structure insulated with basalt wool. This leads to a reduction in the number of temperature transition cycles through zero for materials inside the building envelope, which has a positive effect on their durability and reliability.

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