What a blower door does is measure how airtight a building is by quantifying air leakage and helping locate leaks. It consists of a powerful calibrated fan mounted in a frame that fits into an exterior door opening with a sealed fabric panel. When fan runs, it either depressurizes or pressurizes the house to a standard pressure difference of 50 pascals relative to outdoors, which simulates about 20 mile per hour wind hitting all sides of building at once. The fan's airflow needed to maintain that pressure is measured in cubic feet per minute at 50 pascals, called CFM50, and used to calculate air changes per hour at 50 pascals, ACH50, and natural air changes. This number indicates leakiness, for example 2000 CFM50 means moderately leaky older home while 1000 CFM50 means tight new home. Beyond measurement, blower door helps find leaks, while fan is running you can feel drafts around windows, outlets, attic hatches, and use smoke pencil or infrared camera to pinpoint exact leak locations. Builders and energy auditors use it for code compliance, quality control, energy savings estimates, and verifying air sealing improvements, making it essential tool for building science.
1 votes
Marked as accepted