U-value time series analyses: Evaluating the feasibility of in-situ short-lasting IRT tests for heavy multi-leaf walls

Tejedor, Blanca; Casals, Miquel; Macarulla, Marcel; Giretti, Alberto

doi:10.1016/j.buildenv.2019.05.001

Cited by 21 publications

(9 citation statements)

References 77 publications

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“…Indeed, the thermal gradient through the wall was within the range of 7-10 • C in the case of test without heating. The deviation between the theoretical and measured U-value was 1.24 up to 3.97% for a test duration of 2-3 h. Further research of the same authors allowed evaluating the impact of operating conditions and thermo-physical properties on the quality of the results [32] as well as verifying if non-transient regime have been achieved during in situ tests [33]. The results pointed out that the most favorable range of temperature gradient between inside and outside environment was from 7 to 16 • C, considering unheated buildings and heavy and poorly insulated walls.…”

Section: Quantitative Infrared Thermography Under Steady-state Conditmentioning

confidence: 94%

“…The first NDT technique was carried out according to the procedure extensively reported by Tejedor et al [20], which considers a 1D horizontal heat flux generated by convection and radiation processes under stationary regime. For the real built environment, the recommendations of Tejedor et al [33] and Tejedor et al [34] should be taken into account in terms of operating conditions, thermo-physical properties and test duration. For example, 30 min can be enough for homogeneous samples, while 2-3 h are needed for heterogeneous samples.…”

Section: Laboratory Testing Under Steady-state Conditionsmentioning

confidence: 99%

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Impact of Stationary and Dynamic Conditions on the U-Value Measurements of Heavy-Multi Leaf Walls by Quantitative IRT

et al. 2020

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Infrared thermography (IRT) has become a commonly applied non-destructive testing method for assessing building envelopes. Like any diagnosis tool, IRT requires an appropriate experience and principle understanding, mainly when the method is used for quantitative analyses. The challenges of the IRT often deal with the dynamic properties of building partitions. Climatic conditions have a certain variability, and the accumulated energy storage in the building components can affect their temperature as well as the calculated thermal performance. This paper aims to analyze how stationary and dynamic regimes of a quantitative IRT test could impact the measured thermal transmittance of heavy multi-leaf walls. Investigation in two European countries with different climatic conditions are reported. In this way, it is discussed which boundary conditions should be guaranteed to provide reliable information about a building envelope using quantitative IRT. In order to check the quality of the measurements, the heat flux meter (HFM) method was also implemented, following the ISO 9869. The research revealed that it could be possible to use short-lasting tests in the climatic conditions of Southern Europe, while long-term tests should be implemented in Northern European countries where climatic conditions are less regular.

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Section: Quantitative Infrared Thermography Under Steady-state Conditmentioning

confidence: 94%

Section: Laboratory Testing Under Steady-state Conditionsmentioning

confidence: 99%

Impact of Stationary and Dynamic Conditions on the U-Value Measurements of Heavy-Multi Leaf Walls by Quantitative IRT

et al. 2020

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“…The monitoring process was designed following ISO guidelines [31]. Taking into account the considerations of Asdrubali et al [14], Evangelisti et al [16], Ahmad et al [41], Tejedor et al [49,50], Barreira et al [51] and Nardi et al [52], the placement of equipment was examined with an infrared thermographic camera (FLIR E60bx Infrared Camera). Proximity to defects, joints and borders of the wall, direct solar radiation and direct impact of heating or cooling devices were avoided, as recommended by Guattari et al [42] and Evangelisti et al [53].…”

Section: Instrumentationmentioning

confidence: 99%

Influence of HFM Thermal Contact on the Accuracy of In Situ Measurements of Façades’ U-Value in Operational Stage

2021

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Accurate information on the actual thermal transmittance of walls is vital to select appropriate energy-saving measures in existing buildings to meet the commitments of the European Green Deal. To obtain accurate results using the heat flow meter (HFM) method, good thermal contact must be made between the heat flow meter plate and the wall surface. This paper aimed to assess the influence of the non-perfect thermal contact of heat flow meter plates on the accuracy of in situ measurement of the façades’ U-value when a film was applied to avoid damage to the wall surface. Given the fact that to avoid harm to the wall surface, the laying of a film is a usual procedure in the installation of equipment during the building’s operational stage. The findings show that deviations between measured U-values when an HFM was installed directly on the wall surface and when an HFM was installed with a PVC film were found to differ significantly from the theoretical effect of including a PVC film during the monitoring process.

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“…Quantitative infrared thermography (QIRT) is an alternative NDT for the in-situ measurement of thermal transmittances that solves the limitations of other mentioned methodologies (i.e. endoscopies, data analysis from simulation or building material databases, HFM) [Albatici et al, 2010;Dall'O et al, 2013;Fokaides et al, 2011;Nardi et al, 2014;Tejedor et al, 2017] and requires shorter test periods (only 30 minutes) for homogeneous heavy multi-leaf walls [Tejedor et al, 2019]. In contrast to the HFM, which considers the heat flux due to conduction, QIRT estimates the effect of radiation and convection processes in a stationary regime to assess the U-value.…”

Section: Introductionmentioning

confidence: 99%

Thermographic 2D U-value map for quantifying thermal bridges in building façades

Tejedor

Barreira

Almeida

et al. 2020

Energy and Buildings

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U-value time series analyses: Evaluating the feasibility of in-situ short-lasting IRT tests for heavy multi-leaf walls

Cited by 21 publications

References 77 publications

Impact of Stationary and Dynamic Conditions on the U-Value Measurements of Heavy-Multi Leaf Walls by Quantitative IRT

Impact of Stationary and Dynamic Conditions on the U-Value Measurements of Heavy-Multi Leaf Walls by Quantitative IRT

Influence of HFM Thermal Contact on the Accuracy of In Situ Measurements of Façades’ U-Value in Operational Stage

Thermographic 2D U-value map for quantifying thermal bridges in building façades

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