Iso 9869-1

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ISO9869-1:2014 describes the heat flow meter method for the measurement of the thermal transmission properties of plane building components, primarily consisting of opaque layers perpendicular to the heat flow and having no significant lateral heat flow.

The heat flow meter measurement method is also suitable for components consisting of quasi homogeneous layers perpendicular to the heat flow, provided that the dimensions of any inhomogeneity in close proximity to the heat flow meter (HFM) is much smaller than its lateral dimensions and are not thermal bridges which can be detected by infrared thermography.

ISO 9869-1:2014 describes the apparatus to be used, the calibration procedure for the apparatus, the installation and the measurement procedures, the analysis of the data, including the correction of systematic errors and the reporting format.

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Feature papers represent the most advanced research with significant potential for high impact in the field. A Feature Paper should be a substantial original Article that involves several techniques or approaches, provides an outlook for future research directions and describes possible research applications.

Lee, Ye-Ji, Ji-Hoon Moon, Doo-Sung Choi, and Myeong-Jin Ko. 2024. "Influences of Average Temperature Difference and Measurement Period on Estimation of In Situ Thermal Transmittance of Building Exterior Walls Using the Average Method of ISO 9869-1" Energies 17, no. 5: 1177.

Abstract: In the last few decades, an average method which is regulated by ISO 9869-1 has been used to evaluate the in situ thermal transmittance (U-value) and thermal resistance (R-value) of building envelopes obtained from onsite measurements and to verify the validity of newly proposed methods. Nevertheless, only a few studies have investigated the test duration required to obtain reliable results using this method and the convergence characteristics of the results. This study aims to evaluate the convergence characteristics of the in situ values analyzed using the average method. The criteria for determining convergence (i.e., end of the test) using the average method are very strict, mainly because of the third condition, which compares the deviation of two values derived from the first and last periods of the same duration. To shorten the test duration, environmental variables should be kept constant throughout the test or an appropriate period should be selected. The convergence of the in situ U-value and R-value is affected more by the length of the test duration than by the temperature difference if the test environment meets literature-recommended conditions. Furthermore, there is no difference between the use of the U-value and R-value in determining the end of the test. Keywords: thermal resistance; thermal transmittance; heat flow meter method; average method; convergence characteristics; opaque exterior wall

Choi DS, Ko MJ. Analysis of Convergence Characteristics of Average Method Regulated by ISO 9869-1 for Evaluating In Situ Thermal Resistance and Thermal Transmittance of Opaque Exterior Walls. Energies. 2019; 12(10):1989.

Choi, Doo Sung, and Myeong Jin Ko. 2019. "Analysis of Convergence Characteristics of Average Method Regulated by ISO 9869-1 for Evaluating In Situ Thermal Resistance and Thermal Transmittance of Opaque Exterior Walls" Energies 12, no. 10: 1989.

Calculation of heat transfer in windows has a direct impact on the thermal transmittance on highly insulated glazing components. A series of experimental tests were carried out in order to calculate the U-value of active insulated windows using the Heat Flux Meter method (ISO 9869-1); this to compare the insulation properties of traditional single glass, double glazing with different aerogel fillings and vacuum glazing windows.

The use of this heat flux method utilised an environmental chamber to provide a temperature difference of 15 C reporting the U-values as follows: traditional double glazing 3.09 W/m2K, vacuum glazing 1.12 W/m2K, and double glazing with aerogel pillars 2.52 W/m2K. On the other hand, double glazing with KGM wheat starch reported 3.40 W/m2K, double glazing with granulated aerogel 2.07 W/m2K and heat insulation solar glass 1.84 W/m2K.

Vacuum glazing recorded optimal results under these experimental conditions, describing a U-value 78 % lower when compared to traditional single glazing window units (5.15 W/m2K). Installation of windows with lower thermal transmittance are expected to increase in the global market to meet the current construction codes, aimed for achieving net zero carbon buildings.

Thermal transmittance also known as U-value, is the heat flow rate divided by the area and temperature difference in the surroundings of both sides of a system at a steady state (BSI, 2014); and is a concept utilised to define the insulation properties for building materials. Construction elements with lower U-values are more effective to reduce the energy consumption in buildings due to its capacity to insulate from external weather conditions (usually utilised for colder climates).

This paper evaluates a series of static windows that utilise passive technologies to improve heat and optical performance in buildings. This would be achieved by calculating their thermal transmittance coefficients via experimental process, using the heat flux meter method described in the international standard ISO 9869-1:2014. The paper objective includes analysing the significance and implications for testing windows under standardised conditions, as well as providing experimental results on the application of this code. The analysis aims to report the heat flow and temperatures on the glazing surface, as well as the assessment of thermal imagery and the formulae applied to the experimental setup.

The analysis of building elements in-situ, helps to evaluate their thermophysical properties, their performance for building design, construction and refurbishment. This is applicable in the implementation of thermal comfort and insulation strategies to minimise energy consumption in buildings (Gori et al., 2017). There are several methods for calculating the thermal transmittance in building elements and a summary of the norms for their calculation is listed in Table 1, using the codes for the International Organisation for Standardisation.

For the focus of this experimental process, the selected code was the heat flow meter method (average process) due to its scalability, accuracy and adaptability. Since it is a non-invasive method, it could be adjusted to different glass sizes and save the experimentation process from the use of duplicate specimens. Contrastingly, the size restrictions and measurement periods linked to this standard make this method challenging for achieving a calculation balance. However, the use of infrared thermography helps in the validation of results, comparing the collected data throughout the experimental process (Figure 5).

Considering that a steady state plausible for on-site experimentations, the ISO standards recommends the average method to estimate the thermal transmittance. Their calculation are based on recording the heat flow rate, ambient and interior temperatures for relatively long periods (at least 72 hours). This method is valid only if the heat transfer coefficients are constant during the entire testing period (BSI, 2014).

Using the average method allows a more robust validation of data, being that it assumes the glass transmittance as a quotient of the mean density of heat flow rate, by the mean temperature difference between the interior and exterior sides of the specimen (defined in equation 1). This assumption is only valid however, when the experimentation occurs isolated from direct solar radiation and is carried out at intervals of 0.5 hours for longer periods (BSI, 2014). Calculations of the thermal resistance and conductance of materials are included in equation 2 and 3, accordingly.

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