Ventilation of buildings and homes is a key issue both from comfort and energy aspects. However to determine the average ventilation air flow or the Air Change Rate (ACH) for a heating season by tests in case of natural ventilation, involve certain difficulties. Essential requirements when testing a physical phenomenon:
- The test itself must not influence the tested phenomena.
- The test must be repeatable delivering the same result each time.
Tracer gas test does not influence the tested phenomena but repeated tests do not deliver the same result due to the constantly changing ambient condition e.g. temperature and wind speed affecting the ACH tremendously. Repeated BlowerDoor tests deliver the same result assuming that the wind speed during the tests remains below the threshold, but the ACH evinced by the test is much higher than the normal due to the higher than normal natural test pressure difference. The aim of the research introduced by the paper was to elaborate a method to specify the average ACH for a heating season based on field tests.
- Testing the leakage by BlowerDoor test at +50 and -50 Pa pressure difference, and performing a series of tests at various pressure differences. Plot the correlation curve against logarithmic scale.
- Performing a series of tests to measure the real ACH values by tracer gas technology throughout a whole heating season during various ambient conditions.
- Searching cross correlation between the temperature difference, the wind speed and the real ACH.
- Searching correlation between real ACH values and the BloweDoor test results.
The result of this approximation is a multivariate equation visualised as a surface chart. This equation with the parameters provides a more sophisticated method than the currently available ones to estimate the average ACH for a heating season. The method developed is suitable to estimate the average ACH for various climate zones.