Assessment of the thermal efficiency of external vertical building enclosures

Introduction. The project documentation for the construction of a permanent structure contains a section justifying the building’s energy efficiency. This justification is based on the compliance of its thermal performance parameters with the norms in force in Russia. A key parameter is the thermal of the external building envelope, which serves as a measure of its thermal effectiveness. However, the normative calculation method for this parameter, which relies on a two-dimensional heat transfer analysis, is inadequate for accurately evaluating true thermal performance. Its primary shortcoming is the inability to model all critical heat loss areas — specifically, thermal bridges present in non-uniform envelope assemblies and at structural junctions.

Materials and methods. The paper presents an analysis of the facade system design implemented in a monolithic residential building with balconies, intended for construction in Moscow. The exterior walls are constructed from monolithic reinforced concrete and autoclaved aerated concrete blocks within a ventilated facade system. Thermal performance was assessed via 3D heat transfer modelling using TEPL software.

Results. The analysis of temperature distribution on surfaces has identified specific areas of excessive heat loss within the structures. Corresponding measures for additional insulation have been developed. Calculations performed withthe TEPL software package determined the design thermal resistance of the building envelope assemblies. These results provide a verified assessment of the thermal efficiency for both the original design and the proposed insulated solutions.

Conclusions. The findings advocate for a paradigm shift in practice, proposing that the thermal evaluation of external vertical enclosures should be based on 3D numerical modelling. Such an analysis provides a reliable value for the equivalent thermal resistance and, crucially, maps all thermal bridges, informing necessary design corrections to mitigate them.

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