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Reliability of ductwork airtightness measurement: impact of pressure drop and leakage repartition on the test result

Sylvain Berthault, Valérie Leprince, 2019
ductwork | airtightness | measurement | pressure drop | Ventilation.
Bibliographic info: 40th AIVC - 8th TightVent - 6th venticool Conference - Ghent, Belgium - 15-16 October 2019
Languages: English Pages (count): 14

Building airtightness requirements are becoming more and more common in Europe (Leprince, Carrié, & Kapsalaki, 2017). However, airtight buildings require an efficient ventilation system to ensure good indoor air quality. In France, the inspection of ventilation system (Jobert, 2012) has revealed many noncompliance. They are mainly due to bad conception, poor implementation, and lack of maintenance. This often leads to reduced ventilation flowrates and poor indoor air quality. Leaky ductwork is one of the reasons for this noncompliance. Therefore, in France, a ductwork airtightness test is now mandatory for new building applying to an Effinergie label, and the ductwork shall reach at least the class A. 

Since the test is mandatory and a minimum level required, it raises the question of the reliability of the test. Inside a ductwork a flowrate undergoes pressure drop due to friction and dynamic losses. It is relevant to wonder whether these losses have an impact on the result of the ductwork airtightness test. 

Before the Promevent project, an experiment was conducted to estimate the impact of these losses on the result of the airtightness test. Results were briefly presented at the AIVC 2014 conference (Berthault, Boithias, & Leprince, 2014) and stated that: 

  • the position of the measuring device seemed to have no impact on the result of the airtightness test for various distribution of leakages 
  • only very high dynamic losses (almost completely closed damper) had an impact on the result.

The objectives of this paper are: 

  • to present the experimental set-up and detail the tests carried out
  • to present the developed numerical model to estimate the impact on the result of the airtightness test of friction and dynamic losses according to the level of airtightness.
  • to compare the results obtained with the numerical model and the experimental set-up.

It has been shown that, for airtight ductwork (class C) the impact of pressure losses on the measured flowrate is expected to be very small. 

Nevertheless for very leaky ductwork it would be good practice to define a maximal length to be tested (distance between the measuring device and the farthest end of the ductwork) or to check in various location the homogeneity of the pressure. 

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