Effect of insolation heating of roof coverings on their performance reliability

Introduction. The article addresses the issues of ensuring the performance reliability of warm roofs in terms of condensation moisture accumulating in their structures, which causes leaks on the upper floors of buildings. Such problems are often revealed when buildings are inspected during repair and reconstruction works. Leaks in the ceilings of buildings with warm roofs were detected in dry, sunny weather with significant heating of the roof covering due to solar radiation.

Aim. To examine the effect of the insolation heating of a roof covering on the formation of condensate in the warm roof of a building in summer, taking into account its design solution.

Materials and methods. Materials are presented on inspection of buildings in the Moscow region for repair and reconstruction needs; they reveal the problem of leak formation in the warm roofs of buildings on dry, sunny summer days. The process of moisture transfer through the exterior covering was analyzed through analytical calculations using the roof design solution in the considered structure as an example.

Results. The calculation of moisture transfer yielded vapor transmission resistance, conventional true and maximum partial pressures of water vapor, as well as temperatures at the layer boundaries in the studied structures. Changes in these parameters across the thickness of structures were revealed via a graphical method, which showed where the dew point indicating possible condensation in the covering is formed. For a comparative analysis, moisture transfer was calculated for a similar design in which mineral wool insulation was replaced by extruded polystyrene.

Conclusions. 1. The calculations of moisture transfer in the examined covering designs confirmed the formation of condensate due to the insolation heating of the roof in summer. 2. The choice of a covering design solution in the design of buildings should be based on accurate heat and moisture calculations taking into account climatic conditions in the construction area, including for the summer season.

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