Multiple Parametric Models of Heat Transfer in Lightweight Building Elements with Ventilated Cavities

Lightweight building elements (LBEs) with one or two ventilated cavities are multifunctional building-envelope elements that lower the heat transfer to the ambient and enable solar heating. In the case of two ventilated cavities they operate as recuperative heat exchangers in the building's ventilation system. This paper presents the development of a calculation procedure for the characterisation of such innovative building-envelope elements. Using a commercial numerical tool, a wide range of influential parameters was studied. Based on the numerical results, multiple parametrical models (MPMs) for determining an effective U-value and the heat gains on the supply of ventilation air were developed for the case of an LBE with one ventilated cavity, meanwhile MPMs for calculating the effective U-value and the heat-recovery rate were developed for an LBE with two ventilated cavities. Such MPMs can be integrated into well-known computer tools for buildings' energy-efficiency simulations, for example, TRNSYS. The accuracy of the models was verified with field experiments.