Proposal of a method for predicting the airtightness performance in a high-rise residential building using pressure difference

Abstract

Recently, it is real to recognize the importance of airtightness performance and it has become mandatory to measure airtightness performance measurement through various standards in Korea. In Korea, air tightness performance is measured using blower door test based on pressurization / depressurization method. However, the conventional blower door test has various inconveniences and problems in the measurement. This study propose a method of predicting the airtightness performance by using the pressure difference, which can replace the conventional blower door test method that can measure the airtightness performance. In order to verify the method proposed in this study, the predicted results were compared to the measured results using blower door test. The proposed method is similar to the blower door test when compared to the blower door test, but there are some differences. The blower door test is measured by measuring the air flow at several pressure difference conditions (10 ∼ 70 Pa) and finding C, n. C and n values can be calculated and the airtightness performance can be obtained by knowing the amount of air passing through the building envelope. However, the only way to measure the airflow through the actual building envelope is the blower door test, which is difficult to measure with other methods. This study measured the pressure difference between the front door and the building envelope, which can be easily measured, and calculated the airflow that pass to the building envelope based on the airflow at various pressure difference conditions shown in the airtightness report of the front door. This is possible because the amount of air flowing in and out under steady state conditions is always the same. Based on this, the airflow was calculated at several pressure difference conditions of the building envelope, and C and n were defined. With this, it is possible to calculate the airtightness performance, the leakage area under various pressure difference conditions. In order to verify the proposed method, this study measures the pressure difference and the airtightness performance of the building using the existing method. The results are as follows; the value of C, n was calculated using the proposed method, and C was about 19.4 and n was about 0.895. The airtightness performance was predicted based on the calculated C and n, and the airtightness performance was calculated to be 3.25 (1/h@50 Pa). When the error rate is calculated as NMSE(Normalized Mean Square Error) for the airtightness performance measured by the blower door test and predicted in this study, NMSE is calculated as 0.01, and the method proposed in this study is reliable because it is included in the reliable range of NMSE 0.25. Proposed method is possible to calculate all the values obtained from the existing blower door test. Therefore, the method can replace the blower door test because both C and n values, airtightness performance, and leakage area under various pressure difference conditions can be calculated.