Thermal properties of building walls: Indirect estimation using the inverse method with a harmonic approach

Abstract

This study investigates energy efficiency in buildings. The accurate evaluation of energy consumption in existing buildings is a difficult task, particularly due to the Mediterranean climate, which is in the temperate zone. Among the various analytical models, the most effective measurement of the energy consumption of buildings is the dynamic type. In evaluating the energy consumption of buildings, the greatest contribution is provided by opaque components and particularly by the external walls of that building. In the model, which is reported in the EN ISO 13786, the thermal properties (the specific heat (J/kgK) and thermal conductivity (W/mK) of the layers of the wall were tested, and the technical standard reported that the physical properties (from which they derive the phase shift and decrement factor) transferred through the wall when a sinusoidal wave temperature variation was applied in a periodic steady state. We propose an inverse approach to measure the sinusoidal periodic steady state (temperature and thermal flux) on the two faces of the wall. With this approach, it is possible to obtain the thermal properties of the wall through an inverse analytical model. The model was applied in a real experiment on a full-size wall in a climatic chamber to verify the dynamic thermal and physical properties of the layers.