Advanced search
1 file | 1.14 MB Add to list

On the use of infrared thermographic measurements for evaluating the airtightness of the building envelope

Author
Organization
Abstract
Infrared thermography (IRT) is a non-destructive evaluation technique that can be used to detect construction deficiencies e.g. thermal bridges and moisture problems. Besides, often used in combination with a pressurization fan, IRT allows to detect air leakages in the building envelope. The purpose of this research was to investigate whether it is possible to estimate an air infiltration flow, based on infrared images. This paper discusses IRT performed on a small test house that was built in the laboratory. Air leaks were subsequently created in a controlled manner in the building envelope, e.g. at the roof-wall interface. The amount of air flow through the leaks was determined with a depressurization test. These measurements were combined with thermographic images to visualise the air leakages. The inside and outside temperature conditions were monitored as well. By deriving the temperature factor from the thermographic images, it was possible to compare IRT images made in different circumstances. In this paper, a wall-wall and roof-wall junction are examined. Complementary, numerical simulations were performed to examine the influence of the measurement uncertainty of the air flows and air leak widths on the surface temperatures. The roof-wall and wall-wall junction were modelled with the same temperature difference and measured air flows from the depressurization tests. In addition, the minimum and maximum possible air flows from the 95% confidence interval and two leak widths of 0,5 and 1 mm were simulated. The chosen CHTC-correlation was based on turbulent convection, which is directly related to the air velocity through the leak, and thus to the chosen leak widths. The results showed that the simulated surface temperatures differed maximum ±1,14 °C, when comparing simulations with the maximum possible and measured air flow (m³/s). Secondly, an overestimation of the air leak width resulted in higher simulated surface temperatures. Larger widths leads to lower air velocities and CHTC’s. So in actual practice, an overestimated leak width can lead to an overestimation of the air velocity and thus infiltration flow. In addition, the laboratory observations showed that the configuration of the joints is an important factor to be taken in account when analyzing IRT, since this characteristic determines the air flow path. Future research will be based on improved laboratory measurements, but also the CHTC correlations will be studied closer. The latter parameter strongly depends on the configuration of the joint. E.g. an air leak in a corner will show different CHTC’s inside, in wall-wall junctions the CHTC correlation will vary across the height of the joint. Therefore, further research on this effect is necessary.
Keywords
airtightness, Infrared thermography, building envelope, simulations, measurements

Downloads

  • (...).pdf
    • full text
    • |
    • UGent only
    • |
    • PDF
    • |
    • 1.14 MB

Citation

Please use this url to cite or link to this publication:

MLA
Maroy, Katrien, Nathan Van Den Bossche, Marijke Steeman, et al. “On the Use of Infrared Thermographic Measurements for Evaluating the Airtightness of the Building Envelope.” 1st International Symposium on Building Pathology, Proceedings. 2015. Print.
APA
Maroy, K., Van Den Bossche, N., Steeman, M., Van De Vijver, S., Carbonez, K., & Janssens, A. (2015). On the use of infrared thermographic measurements for evaluating the airtightness of the building envelope. 1st International Symposium on Building Pathology, Proceedings. Presented at the 1st International Symposium on Building Pathology (ISBP-2015).
Chicago author-date
Maroy, Katrien, Nathan Van Den Bossche, Marijke Steeman, Sven Van De Vijver, Kim Carbonez, and Arnold Janssens. 2015. “On the Use of Infrared Thermographic Measurements for Evaluating the Airtightness of the Building Envelope.” In 1st International Symposium on Building Pathology, Proceedings.
Chicago author-date (all authors)
Maroy, Katrien, Nathan Van Den Bossche, Marijke Steeman, Sven Van De Vijver, Kim Carbonez, and Arnold Janssens. 2015. “On the Use of Infrared Thermographic Measurements for Evaluating the Airtightness of the Building Envelope.” In 1st International Symposium on Building Pathology, Proceedings.
Vancouver
1.
Maroy K, Van Den Bossche N, Steeman M, Van De Vijver S, Carbonez K, Janssens A. On the use of infrared thermographic measurements for evaluating the airtightness of the building envelope. 1st International Symposium on Building Pathology, Proceedings. 2015.
IEEE
[1]
K. Maroy, N. Van Den Bossche, M. Steeman, S. Van De Vijver, K. Carbonez, and A. Janssens, “On the use of infrared thermographic measurements for evaluating the airtightness of the building envelope,” in 1st International Symposium on Building Pathology, Proceedings, Porto, Portugal, 2015.
@inproceedings{6862008,
  abstract     = {Infrared thermography (IRT) is a non-destructive evaluation technique that can be used to detect construction deficiencies e.g. thermal bridges and moisture problems. Besides, often used in combination with a pressurization fan, IRT allows to detect air leakages in the building envelope. The purpose of this research was to investigate whether it is possible to estimate an air infiltration flow, based on infrared images.
This paper discusses IRT performed on a small test house that was built in the laboratory. Air leaks were subsequently created in a controlled manner in the building envelope, e.g. at the roof-wall interface. The amount of air flow through the leaks was determined with a depressurization test. These measurements were combined with thermographic images to visualise the air leakages. The inside and outside temperature conditions were monitored as well. By deriving the temperature factor from the thermographic images, it was possible to compare IRT images made in different circumstances. In this paper, a wall-wall and roof-wall junction are examined.
Complementary, numerical simulations were performed to examine the influence of the measurement uncertainty of the air flows and air leak widths on the surface temperatures. The roof-wall and wall-wall junction were modelled with the same temperature difference and measured air flows from the depressurization tests. In addition, the minimum and maximum possible air flows from the 95% confidence interval and two leak widths of 0,5 and 1 mm were simulated. The chosen CHTC-correlation was based on turbulent convection, which is directly related to the air velocity through the leak, and thus to the chosen leak widths. 
The results showed that the simulated surface temperatures differed maximum ±1,14 °C, when comparing simulations with the maximum possible and measured air flow (m³/s). Secondly, an overestimation of the air leak width resulted in higher simulated surface temperatures. Larger widths leads to lower air velocities and CHTC’s. So in actual practice, an overestimated leak width can lead to an overestimation of the air velocity and thus infiltration flow. In addition, the laboratory observations showed that the configuration of the joints is an important factor to be taken in account when analyzing IRT, since this characteristic determines the air flow path. 
Future research will be based on improved laboratory measurements, but also the CHTC correlations will be studied closer. The latter parameter strongly depends on the configuration of the joint. E.g. an air leak in a corner will show different CHTC’s inside, in wall-wall junctions the CHTC correlation will vary across the height of the joint. Therefore, further research on this effect is necessary.},
  author       = {Maroy, Katrien and Van Den Bossche, Nathan and Steeman, Marijke and Van De Vijver, Sven and Carbonez, Kim and Janssens, Arnold},
  booktitle    = {1st International Symposium on Building Pathology, Proceedings},
  keywords     = {airtightness,Infrared thermography,building envelope,simulations,measurements},
  language     = {eng},
  location     = {Porto, Portugal},
  pages        = {8},
  title        = {On the use of infrared thermographic measurements for evaluating the airtightness of the building envelope},
  year         = {2015},
}