Evaluating the Energy Performance of Historic Buildings: Experimental Methodology for the Analysis of Heat Transfer in the Surface Boundary Layers of Wall Assemblies

Energy performance represents a major focus in building engineering, with an increasingly marked urgency arising over the last decades due to growing environmental concerns. The European Union nowadays stresses the importance of energy efficiency and decarbonisation of the existing building stock through the implementation of adequate mitigation strategies addressing climate changes and energy transition [1]. In this perspective, historical constructions, constituting a conspicuous percentage of the built environment, are very relevant and present indeed huge energy-saving potential. This study aims at evaluating the energy performance of buildings with particular insights on adequate optimisation of thermal insulating capabilities of historical constructions. More specifically, the paper focuses on ongoing experiments carried out in a climatic wind tunnel, based on past results [2, 3], where several types of building envelopes are tested monitoring their responses to realistic climatic scenarios. The experimental data obtained ensure describing the interrelationship among various parameters such as temperature, relative humidity, wind velocity and direction as well as heat fluxes in the building component and surface roughness. The main objective is to describe the heat transfer in the mixed velocity-thermal boundary layer near the envelope surfaces. For that purpose, convective heat transfer coefficients for various types of envelopes are determined under different environmental conditions using a combined experimental-computational method, as in e.g. [4]. The obtained outputs are exploited in energy simulation models and heat transfer simulations to achieve higher accuracy than standardized methods. Future work is also outlined in the perspective of bettering energy performance and its evaluation in historic buildings.