Abstract
The measurement of ventilation rates is crucial in understanding buildings’ performances, but can be a rather complex task due to the time-dependency of wind and buoyancy forces, which are responsible for the pressure differences that induce air movement across the envelope. Thus, assessing air change rate through one-time measurements during brief periods of time may not be a reliable indicator. In this paper, the variability in the measurement of ventilation rates using the decay technique was evaluated. To that end, two compartments of a typical single-family detached dwelling were selected as a case study and 132 tests were performed, considering two different boundary conditions (door closed and door open). This work allowed the large variability of the results to be highlighted, as the coefficient of variation ranged from 20% to 64%. Wind speed had a key effect on the results, especially because during the measurements indoor–outdoor temperature differences were not so significant. The possibility of using occupant-generated carbon dioxide as tracer gas was also analyzed, but problems of cross-contamination were identified.
Highlights
The importance of buildings’ ventilation is enhanced by the growing energy concerns across the European Union [1,2], pointing to a reduction of the energy demand for ventilation
The air movement required for natural ventilation occurs due to pressure differences produced by the combined effect of wind and buoyancy forces, which are both time-dependent [8]
This paper aims to evaluate the variability in the measurement of ventilation rates using the decay technique and two different tracer gases
Summary
The importance of buildings’ ventilation is enhanced by the growing energy concerns across the European Union [1,2], pointing to a reduction of the energy demand for ventilation. The ventilation rate is relevant in the context of mild climate countries where window opening is the main source for fresh air admission and is highly influenced by user behavior [5,6,7]. In mild climate countries, natural ventilation is the most common strategy. The air movement required for natural ventilation occurs due to pressure differences produced by the combined effect of wind and buoyancy forces, which are both time-dependent [8]. Due to the unstable conditions that occur outdoors (wind and air temperature), one-time measurements of the ventilation rate, made over a short period, may not be an accurate indicator of the performance of the building [9,10,11]
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