Abstract
This paper proposes an alternative experimental procedure that uses infrared thermography (IRT) for measuring the surface temperature of building elements, through which it is possible to approximate the thermal transmittance or the U-value. The literature review showed that all authors used similar procedures that require semi-stationary heat transfer conditions, which, in most cases, could not be achieved. The dynamic and the average methods that are given in ISO 9869 were also used with the IRT and the heat flux method (HFM). The dynamic method (DYNM) shows a higher level of accuracy compared to the average method (AVGM). Since the algorithm of the DYNM is more complicated than that of the AVGM, Microsoft Excel VBA was used to implement the algorithm of the DYNM. Using the procedure given in this paper, the U-value could be approximated within 0–30% of the design U-value. The use of IRT, in combination with the DYNM, could be used in-situ since the DYNM does not require stable boundary conditions. Furthermore, the procedure given in this paper could be used for relatively fast and inexpensive U-value approximation without the use of expensive equipment (e.g., heat flux sensors).
Highlights
A building’s external envelope represents the barrier that separates the outer and inner environment, and its purpose is to protect the users from external atmospheric conditions
For Wall 2 that was true for two-days measurement period where the difference was approximately 0.16%–7.19% (Figure 10), and for one day measurement period the difference was 120% (Figure 10) which might have been caused by direct solar radiation on the thermocouples and indirect radiation reflected from the windows that were overheated by sunlight
This paper shows that there is potential for using the infrared thermography (IRT) for calculating the U-value in real environmental conditions in-situ
Summary
A building’s external envelope represents the barrier that separates the outer and inner environment, and its purpose is to protect the users from external atmospheric conditions. It needs to provide healthy and comfortable internal environmental conditions for building occupants through its hygrothermal properties, defined by carefully selected materials arranged in the proper order [1]. Heat losses through a building’s external envelope represents a significant percentage of the building’s total energy consumption—the building sector is accountable for circa 32% of final energy consumption [2]. A building’s thermal properties are determined by the thermal transmittance (U-value (W/m2 K)), which is the initial parameter for determining the heating and cooling energy demands [3]. For surface elements (like walls, slabs and roofs) the U-value is determined from Fourier’s and Stefan–Boltzmann’s laws (conduction and radiation, respectively) and Newton’s law of cooling (convection). If one-dimensional heat flow is assumed, the U-value is determined as the inverse value of the overall thermal resistance, according to ISO 6946 [4]—Equation (1): Xn
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
