Infrared thermography technique as an in-situ method of assessing heat loss through thermal bridging

Abstract

A key aspect in assessing the thermal standard of building envelopes is the quantification of the heat loss though thermal bridging, which can be expressed in terms of the linear thermal transmittance Ψ. Values of Ψ may be obtained from tabulated values for standard building details, from numerical modelling or from measurement. Where the internal structure of the building envelope is unknown, which is very often the case, measurement is the only option. This study shows how the infrared thermography technique (ITT) can be used as a non-invasive and easy-to-use method to provide quantitative measures of the actual thermal bridging performance. The novelty of this approach includes evaluation of the actual heat flow rate caused by thermal bridge qTB and Ψ-value by means of the ITT solely, without any supporting methods. Another important aspect of the methodology is that it accounts for the correlation between the surface temperature and the convective and radiative heat transfer coefficients. Values for these coefficients are assessed for the whole range of the surface temperatures recorded on the thermogram resulting in improve accuracy. The qTB and Ψ-value calculated using the presented methodology fully mirrors the real thermal performance of the thermal bridge. The methodology has been tested under laboratory conditions in a steady state in a hot box with excellent agreement.

Laboratory and in-situ non-destructive methods to evaluate the thermal transmittance and behavior of walls, windows, and construction elements with innovative materials: A review

“…In fact, this research gap was also pointed out by Ascione et al [137]. In this context, O'Grady et al [80] proposed a new non-invasive and easy-to-use IRT methodology for the in-situ assessment of the heat loss through a thermal bridgea concrete column in a brick wall. The methodology was tested under laboratory steady-state conditions in a HB apparatus.…”

“…By analyzing the IRT image, it is possible to identify the location of the plastic wall plugs of the ETICS system. In fact, as suggested by O'Grady et al [80], the IRT can be very helpful to define the correct locations for HFM sensors, since these sensors must be located in a place without any inhomogeneities or defects that may lead to incorrect results of the overall U-value of the construction element. Other authors have used IRT as a qualitative tool to select the right place for the location of HFM sensors, such as Asdrubali et al [81], Evangelisti et al [82] and Asdrubali et al [83].…”

“…Other studies that have highlighted the potential of the GHB apparatus to estimate the overall thermal transmittance of LSF assemblies can be found in literature, for instance, the works carried out by Soret et al [169] and Amundarain [170]. The IRT method described by O'Grady et al [80] can also be used for the U-value measurement of LSF walls.…”

The conditions for thermographic testing of thermal power engineering installations

“…The infrared thermography is widely used in various research areas. This statement is confirmed by references [17][18][19][20][21][22], review papers [23,24] and works related to the assessment of this method [25][26][27]. In particular, the favourable features include as follows (for this method):…”

A termografia infravermelha como um ensaio não destrutivo para a inspeção de pontes de concreto armado: Revisão do estado da arte

“…A termografia passiva não requer fontes de estimulação externa (Oh et al, 2013), usa a energia solar e a temperatura ambiente como principais recursos de aquecimento, e é a técnica utilizada para inspeção de pontes (Kee et al, 2012;Vaghefi et al, 2012;Alfredo-Cruz et al, 2015), bem como para outras estruturas e outros campos (Buyukozturk, 1998;Lahiri et al, 2012;Barreira;Almeida;Delgado, 2016;Fox;Goodhew;Wilde, 2016;O'Grady;Lechowska;Harte, 2016). Em contraste, a termografia ativa requer fontes externas de estimulação de calor (Kee et al, 2012;Rehman et al, 2016), pode até ser sub-dividida de acordo com a natureza da estimulação como: Pulsed, Lock-in, Pulsed-Phase, entre outros (Maldague, 2001).…”