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

Ye-Ji Lee, Ji-Hoon Moon, Doo-Sung Choi and Myeong-Jin Ko ()
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Ye-Ji Lee: Department of Architectural Design and Engineering, Incheon National University, Incheon 22012, Republic of Korea
Ji-Hoon Moon: Department of Architectural Design and Engineering, Incheon National University, Incheon 22012, Republic of Korea
Doo-Sung Choi: Department of Building Equipment System and Fire Protection Engineering, Chungwoon University, Incheon 22100, Republic of Korea
Myeong-Jin Ko: Department of Building System Technology, Daelim University College, Anyang 13916, Republic of Korea

Energies, 2024, vol. 17, issue 5, 1-16

Abstract: Many studies have sought to overcome the two main limitations of the average method of ISO 9869-1—its long test duration and low accuracy. These studies reported that the reliability of the results is dependent on the temperature differences. This consensus was based on the results of studies that measured a few cases with specific temperature differences, and the convergence criteria utilized for the representative thermal transmittance (U-value) were rarely examined. This study analyzed the influence of the average temperature difference and test duration on the convergence characteristics and accuracy of U-value estimation using the average method. Data from a north-facing exterior wall with a theoretical U-value of 0.145 W/m 2 ·K were measured between June 2022 and May 2023. The influences of different measurement conditions were analyzed for cases divided based on four measurement periods and 11 average air temperature differences. The findings show that an accurate U-value can be obtained from 7 days’ worth of measurement data with an average temperature difference of 10 °C or higher and that the improvement in accuracy is minimal under stricter conditions. To achieve a convergence probability of over 90% for temperature differences of 10 °C or greater, the second and third criteria required measurement periods of 7 and 15 days respectively.

Keywords: thermal transmittance; average temperature difference; measurement period; average method; building exterior wall (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2024
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