ASTM E779 is a standard test method used to determine the air leakage rate of a building. This method, issued by the ASTM, involves the use of a blower door, which is a special fan that is attached to an exterior door of the building. The blower door is used to create a pressure difference between the inside and outside of the building, which allows for the measurement of air leakage. The purpose of this test is to identify areas of the building envelope where air leakage is occurring, so that the building can be properly sealed and insulated to improve energy efficiency and indoor air quality. ASTM E779 is one of the three standards that New York State has approved for testing residential air leakage.
To perform the blower door test, the building must first be closed up and sealed as much as possible. All windows and doors must be closed, and all exhaust fans must be turned off. The blower door is then installed in one of the exterior doors of the building. The blower door consists of a frame that fits snugly into the doorframe, and a powerful fan that is mounted inside the frame. The fan is used to depressurize the building by pulling air out of the building and blowing it outside. The blower door also has a pressure gauge and a flow meter that are used to measure the pressure difference and the amount of air being moved.
Once the blower door is installed and running, the pressure difference is measured at a standard reference pressure of 50 Pascals (Pa). The pressure difference is the difference in pressure between the inside of the building and the outside of the building. The blower door fan is then adjusted to maintain this pressure difference, and the amount of air being moved by the fan is measured. This measurement is used to calculate the air leakage rate of the building, which is expressed in terms of air changes per hour (ACH). The ACH is a measure of how many times the entire volume of air inside the building is replaced in one hour.
The blower door test is an essential tool for evaluating the energy efficiency of a building and identifying areas where air leakage is occurring. By identifying these areas, steps can be taken to seal and insulate the building envelope, which can significantly reduce energy consumption and improve indoor air quality. ASTM E779 is a widely recognized and accepted standard test method for conducting blower door tests, and is commonly used in building energy codes and standards.