Permeability Measurements of a Passive House During Two Construction Stages

Usually air permeability is measured for a specific building only once: either when the building construction is was just finished or when the building is already in use. In this paper we present a novel aspect. We researched if there is any variation of the building permeability during its construction. We followed the evolution of the building airtightness during the construction of a passive house carrying out permeability measurements in two different phases: (1) airtight construction but not finished and without HVAC, and (2) finished construction with HVAC. For each phase, we used a blower door experiment stand to measure the airflow at different indoor-outdoor pressure differences in two conditions (depressurization and pressurization). We obtained air change rate at 50 Pa well below the maximum limit characteristic to passive house. However an intriguing result was found: the measured permeability for the finished building is slightly bigger than the measured permeability for the unfinished building. On one side the better finishing of the walls and windows lead to an airtightness improvement, but on the other side the new HVAC wall penetrations and HVAC terminals (inlets and exhausts) lead to an airtightness aggravation just enough to turn over the improvement brought by the better state of building finishing.