Numerical modelling of coupled heat, air and moisture transfer in building envelopes

Nadia Laredj,Hassan Naji,Hanifi Missoum,Mustapha Maliki,Karim Bendani

doi:10.1051/meca/2015033

Abstract

This paper reports on numerical modeling of heat, air, and moisture transfer through multilayered walls. Building materials are often subjected to temporal climatic variations, which can induce a transfer of heat and moisture through the walls of the building and the foundation soil. These materials are generally considered as porous media. The coupled heat, air and moisture transfer in building materials is of paramount importance in the construction area. In this way, a mathematical model has been elaborated and validated using a benchmark example. Here, we aim to determine the energy losses. The capillary pressure is considered as potential moisture which represents both the transport of vapor and liquid phases of the water. Basing on basic functions of partial differential equations (PDE’s), one can convert certain measurable properties of porous media as coefficients depending on the temperature and the capillary pressure. The results obtained compare favourably with other available in the literature.

Highlights

Energy consumption by the building sector constitutes a large portion of global energy use
The model accommodates non-linear transfer and storage properties of materials, moisture transfer by vapor diffusion, capillary liquid water transport and convective heat and moisture transfer through multi-layered porous media
The partial-differential equations (PDEs) are derived in such a way that each PDE is described with a single driving potential, which is continuous across the interfaces of adjoining materials

Summary

Introduction

Energy consumption by the building sector constitutes a large portion of global energy use. Energy-efficient building technologies help to reduce heat gain in hot summer months, heat loss in cold winter months, and modify energy requirements in buildings [1]. The moisture transferring in building materials can cause serious results as metal corrosion, structure deterioration and decreasing performance of building insulations. The expansion and deformation of building envelope framework during freezing process have an important impact on building durability and energy consumption in the cold regions. The study on heat and moisture transfer of building envelope is of great important.

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Conclusion