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A blower door is a diagnostic tool used in building energy efficiency assessments to measure and locate air leaks in a structure, such as a house or commercial building. The blower door test helps identify areas where there’s significant air infiltration or exfiltration, which can lead to energy waste, uncomfortable indoor conditions, and increased utility bills.
Here’s how a blower door works:
1. Setup: The blower door consists of a powerful fan that is installed in an exterior door frame or another opening in the building envelope. The fan is typically equipped with adjustable speed controls to vary the air pressure generated.
2. Pressurization and Depressurization: The blower door can operate in two modes: pressurization and depressurization. In the pressurization mode, the fan blows air into the building, increasing the indoor air pressure relative to the outdoors. In the depressurization mode, the fan exhausts air from the building, reducing the indoor air pressure.
3. Measuring Airflow: To quantify the amount of air leakage, the blower door is connected to a manometer, which measures the pressure difference between the indoor and outdoor air. The blower door’s fan is then operated at a specific speed to maintain a constant pressure difference between the indoor and outdoor environments.
4. Calculating Air Leakage: By monitoring the fan speed and the pressure difference, the blower door calculates the airflow rate required to maintain the pressure difference. This airflow rate is a direct measure of the air leakage in the building envelope. The blower door technician can then calculate the Air Changes per Hour (ACH), which indicates how many times the building’s air volume is replaced in an hour due to leaks.
5. Locating Air Leaks: During the blower door test, the technician uses various methods to detect and locate air leaks. These methods can include feeling for drafts with a hand, using a smoke pencil to visualize air movement, or using an infrared camera to identify temperature differences caused by air leaks.
6. Sealing Recommendations: The blower door test results help identify the specific areas where air leaks are occurring. Based on these results, the building occupants or energy efficiency professionals can prioritize sealing or insulating these areas to reduce air leakage and improve energy efficiency.
Blower door tests are a crucial part of energy audits, weatherization projects, and green building certifications. They provide valuable information about a building’s envelope performance, helping occupants make informed decisions to increase energy efficiency, indoor comfort, and overall building performance.
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