Michele Libralato

Michele Libralato

Researcher at University of Udine

Publications

You can also find my articles on my Google Scholar profile and on IRIS.

Effects of considering moisture hysteresis on wood decay risk simulations of building envelopes

Published in Journal of Building Engineering, 2021

Wood decay risk assessment of building envelopes is commonly performed by engineers, architects and practitioners using results of Heat and Moisture Transfer (HMT) simulations and damage models. The commonly accepted HMT models use bijective sorption functions, accepting that materials reach hygrothermal equilibrium with the humidity contained in the air of the material’s pores and of the environment at a single MC. On the other hand, due to moisture hysteresis, equilibrium can be reached at different MCs for the same air condition, depending on previous equilibrium states. The aim of this work is to quantify the effect of considering hysteresis in HMT simulations and to evaluate its propagation in the risk assessment procedure for the case of wood decay. The software MATCH is used, implementation of an HMT model with hysteresis. Three timber walls are simulated in seven locations (Bolzano, Copenhagen, Hong Kong, Ottawa, Shanghai, Udine, and Vienna), first with hysteresis and then with simplified bijective sorption functions (adsorption, desorption, and mean sorption curve). MC and temperature time series are used to perform wood decay risk assessment with two damage models. The results show that the influence of hysteresis can be relevant, and that the choice of the sorption curve used in the simulations should be discussed. For the case of a CLT wall in Shanghai, simulated using the adsorption curve, a mean difference of 1.6% MC is found from the hysteresis case. This resulted in a difference of 0.7 decay rating in 10 years and 6% mass loss in 30 years.

Recommended citation: Libralato M, De Angelis A, Saro O, Qin M, Rode C (2021). Effects of considering moisture hysteresis on wood decay risk simulations of building envelopes. Journal of Building Engineering (Elsevier, 2021). https://doi.org/10.1016/j.jobe.2021.102444

Design and Evaluation of Extreme Moisture Reference Years for Moisture-Related Risk Assessments

Published in Proceedings of Building Simulation Applications BSA 2019, pp.191-199;, 2020

The risk analysis of moisture-related damages can potentially be carried out with the use of heat and moisture transfer simulations. These models require weather files as boundary conditions but, for most locations, the only weather files available are Typical Reference Years, for instance the TRY EN defined in accordance with EN ISO 15927-4:2005. These reference years do not provide the critical conditions that should be used in risk assessments. In this work, two procedures to define Extreme Moisture Reference Years (ERY m1 and ERY m2) are presented. ERYm1 and ERYm2 are designed to generate critical weather files to be used in simulations for the assessment of moisture related risks. The presented procedures are structure-independent and suitable for risk assessments that involve high air moisture content and low air temperature values. In order to assess the capabilities of ERY m, five types of walls with different materials are simulated, considering three Italian climates (those of Gemona del Friuli, of Legnaro and of Trento) and four wall orientations (North, East, South, West). The results of simulations with ERYm1 and ERYm2 as weather files showed higher wall moisture contents and interstitial moisture accumulation risks than those with TRY EN. This suggests that ERY m could be used as a valid alternative to the TRY EN in decision making frameworks and legislations that cannot include the ad hoc definition of a weather file for each structure, exposure and location.

Recommended citation: Libralato, Pernigotto, G., Prada, A., De Angelis, A., Saro, O., & Gasparella, A. (2020). Design and Evaluation of Extreme Moisture Reference Years for Moisture-Related Risk Assessments. Proceedings of Building Simulation Applications BSA 2019, 191–199. https://doi.org/10.13124/9788860461766_24 https://bia.unibz.it/esploro/outputs/991006493993401241

Evaluation of the ground-coupled quasi-stationary heat transfer in buildings by means of an accurate and computationally efficient numerical approach and comparison with the ISO 13370 procedure

Published in Journal of Building Performance Simulation, 2019

The purpose of this article is to present and validate a computationally efficient numerical approach for the calculation of the ground-coupled heat transfer in buildings with periodic boundary conditions. When the boundary conditions of the heat transfer problem are described by periodic functions, it is possible to consider the transient state problem as a quasi-stationary problem with considerable savings in terms of computational time. The method is presented in detail from a mathematical point of view, together with a validation for two simple cases of slab-on-grade thermal losses, four comparisons with the ISO 13370:2007 procedure, a case with a complex shape and an evaluation of the computational efficiency.

Recommended citation: M. Libralato, A. De Angelis & O. Saro (2019) Evaluation of the ground-coupled quasi-stationary heat transfer in buildings by means of an accurate and computationally efficient numerical approach and comparison with the ISO 13370 procedure, Journal of Building Performance Simulation, 12:5, 719-727, DOI: 10.1080/19401493.2019.1628304 https://doi.org/10.1080/19401493.2019.1628304