Correlation analysis between ACH50 and Air permeability considering the floor area of a residential buildings

Airtightness is presented through various expression according to the standards and measurement methods of each country. To compare the airtightness of buildings of different sizes, ACH50 and air permeability are mainly used to express the airtightness.
ACH50 and air permeability are airtightness expression methods calculated by dividing air flow into volume and surface area, respectively. As the size of a building increases, the airtightness value tends to decrease. However, the rate of change of ACH50 and air permeability according to the size of the building appears different, and it is necessary to compare the airtightness with an appropriate expression considering the characteristics of the building.
In this study, to analyze the correlation between ACH50 and air permeability according to the characteristics of the building, airtightness measurement data in multi-unit residential buildings were analyzed. The measurement target was a residential building built with the same construction method, and it was divided into three cases of small, medium, and large sizes, and 24 units were measured for each case.
As a result, the s/v ratio of the large floor area was 1, but the s/v ratio of the small floor area was 1.1. The S/V ratio tends to decrease as the floor area increases, and the area of the target building showed an s/v ratio close to 1, ranging from 1.02 to 1.11. This means that the larger the floor area, the smaller the effect of the airtightness expression. In the case of a small floor area, since the change in the value of ACH50 is relatively large, it is necessary to consider setting detailed standard for ACH50 according to the floor area. When the area is decreased to less than 100 m2 or increased to more than 200 m2, the change rate value is significantly different from 0.8 to 1.5, so it is necessary to evaluate the airtightness results considering the s/v ratio change rate by floor area.