On the effect of material uncertainties in envelope heat transfer simulations

Abstract

The accuracy of energy simulation codes is considerably increasing and it follows that the inputs need to be properly defined and technically characterized. Despite the vast research on uncertainty and sensitivity analysis, little is known about the extent to which a single thermophysical property affects the simulation outcomes. This information can guide the manufacturers of building materials towards improved quality controls and the energy modelers to deeply investigate the input data. This study focuses on the effect of uncertain thermophysical properties on the numerical solutions of the heat equation. A sensitivity analysis applied to several walls in different climates is carried out by using a Monte Carlo technique. Furthermore, the uncertainty propagation is investigated in the finite difference method (FD) and in the conduction transfer functions approach (CTF). For some configurations this study points out that the aleatory uncertainty of the material properties and the climatic boundary conditions have a synergistic effect on the precision of the model predictions. For the other cases, however, it becomes evident that the result precision depends only on both the variability of the thermophysical data and the model accuracy but not on the climate

A comprehensive experimental approach for the validation of quantitative infrared thermography in the evaluation of building thermal transmittance

“…and building materials manufacturers to ensure the minimum deviation as possible between designed and real building energy performance, in order to achieve the Union's 2020 20% headline. Prada et al [4] showed that, among the thermo physical properties of the building envelope, the uncertainty concerning thermal conductivity as input data for energy simulation is what mostly affects the final output accuracy during the design phase concerning heat losses, both outward during winter and inward during summer. Just to evaluate the as-built performance of buildings concerning the U-values of the envelope, in the last 5 years several researchers, other than the authors, used quantitative ITT leading to interesting results.…”

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“…Previous research on the uncertainty of simulation predictions concluded that the reliability of simulation outcomes depends on the accuracy and precision of input data, simulation models and the skills of the energy modeller [43][44][45][46]. An estimation of the uncertainty introduced by each of the aforementioned factors can help to increase the awareness of the results reliability.…”

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