Review of criteria for determining HFM minimum test duration

Gaspar, Kàtia; Casals, Miquel; Gangolells, Marta

doi:10.1016/j.enbuild.2018.07.049

Cited by 28 publications

(11 citation statements)

References 38 publications

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“…This tendency is commonly confirmed in the R-values in Table 4. These results are in good agreement with the results in previous studies in [7,12,16,28], showing that an increase in the measurement period improves the measurement accuracy. Table 4.…”

Section: Evolution Of R-value and U-valuesupporting

confidence: 92%

“…According to the ISO 9869-1 standard [4], the end of the test should be determined using the R-value calculated from the surface temperature difference across the test wall. However, even though the difference between the use of the two values in determining when to terminate the test is not clearly known, several researchers [7,8,12,16] used the U-value instead of the R-value. An estimate of the R-value is obtained as follows:…”

Section: Discussionmentioning

confidence: 99%

“…The simulation results also indicated that the R-values for the two summer scenarios in July showed the limited validity of the average method. Gaspar et al [16] evaluated the minimum duration of in situ experimental campaigns to measure the U-value of the façades of existing buildings using the heat flow meter method. They determined the minimum test duration according to the criteria of data quality and variability of results proposed in ASTM C1155 [17] and the three convergence conditions described in ISO 9869-1 [4].…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

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

Choi

2019

Energies

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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.

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Section: Evolution Of R-value and U-valuesupporting

confidence: 92%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

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

Choi

2019

Energies

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“…The duration of the test was evaluated considering the requirements established in the ISO 9869-1:2014 standard [31,56]. The three requirements are summarised in the following equations (Equations ( 3)-( 5)):…”

Section: Discussionmentioning

confidence: 99%

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

2021

Self Cite

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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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“…The heat flow meter method and the thermometric method have several operational requirements that limit obtaining representative results of the thermal transmittance [28]. The duration of the test [40], the analysis of north-facing walls [41], the moisture content [42], the direction of the heat flow [43], the post-processing of the data [44] and the location of the probes [36] are some of these requirements. However, one of its main aspects included in many studies is the need for having a high thermal gradient (i.e., a high temperature difference between the internal and external temperatures).…”

Section: Introductionmentioning

confidence: 99%

Assessing the Environmental Impact of Thermal Transmittance Tests Performed in Façades of Existing Buildings: The Case of Spain

Bienvenido-Huertas

2020

Sustainability

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Thermal transmittance tests constitute an appropriate tool to assess the energy performance of existing buildings. The heat flow meter method and the thermometric method are the most used experimental methods. One of the main criteria to guarantee appropriate test conditions and the representation of results is to ensure a high thermal gradient. For this purpose, heating or air conditioning systems should be used from three to seven days. Most studies related to experimental methods have addressed the appropriate test conditions; however, the environmental impact related to these conditions have not been analyzed. This study analyzes the energy consumption and the CO2 emissions related to the conditions of the thermal gradient required for tests. An energy analysis of 129,600 cases located in Spain was conducted. The results showed that heating systems are the best option to perform thermal transmittance tests, whereas air conditioning systems do not guarantee appropriate test conditions. As for the energy consumption and the percentage of hours with an appropriate thermal gradient, the adequacy of the heating setpoint temperature according to the predicted estimations of the external temperature during tests would mitigate their environmental impact. The reason is that, in certain cases, the increase of the setpoint temperature does not improve test conditions. Also, the use of heating systems would imply short test durations. Finally, the selection of small rooms with a small façade length would reduce the percentage of CO2 emissions between 31.37% and 36.1%. The results of this study could guarantee a more sustainable performance of thermal transmittance tests. In addition, the results could be used to perform life cycle analysis on buildings where thermal transmittance tests are performed.

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Review of criteria for determining HFM minimum test duration

Cited by 28 publications

References 38 publications

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

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

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

Assessing the Environmental Impact of Thermal Transmittance Tests Performed in Façades of Existing Buildings: The Case of Spain

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