Modeling of Unsteady Heat Transfer through Building Envelopes with Light Ventilated Facades and Roofs

Enclosing structures of buildings constantly change external thermal conditions, which leads to changes in the internal thermal microclimate of premises, which must be taken into account when designing thermal protection of buildings and engineering systems for heating, ventilation and air conditioning. Building envelopes contain ventilated facades and/or roofs with a ventilated gap. In most known research results and calculation methods of the heat transfer through structures is not fully and accurately taken into account due to the complexity of its mechanism, non-stationary external thermal effects. The reason is the low efficiency and accuracy of calculation methods. Purpose: The creation of the effective physical and mathematical model that allows calculating non-steady heat transfer through wall enclosures and coatings containing light facades with a ventilated gap. Methodology: A combined analytical and numerical model is proposed for the heat transfer through wall enclosing structures and coatings containing a ventilated facade. The model includes an iterative calculation of non-stationary heat transfer in a ventilated gap using balance equations of non-stationary heat in a ventilated layer, taking into account the finite-difference detailed calculation of non-stationary heat transfer in the enclosing structure. Research findings: Based on the proposed model, good agreement is shown for experimental data and theoretical calculations. For the model testing, the heat gain into the room through a light ventilated facade and in its absence are considered. It is shown that in summer, the ventilated facade allows for a significant heat reduction in the room, despite an insignificant change in the heat transfer resistance.