How do you calculate the maximum air leakage reduction in CFM for a blower door test?

To determine the maximum air leakage reduction in cubic feet per minute (CFM) during a blower door test, it is essential to understand the roles of the initial reading and the measured volumetric reduction (MVR). The initial reading represents the amount of air leakage at the start of the test, while the MVR indicates the volume of air that is no longer escaping due to reductions made (like sealing leaks).

The correct method to calculate the maximum air leakage reduction involves subtracting the MVR from the initial reading. This calculation reveals the remaining air leakage rate after accounting for the volume that has been reduced. By emphasizing the reduction, you can quantify how effective the air sealing measures have been. Therefore, by subtracting the MVR from the initial reading, you accurately assess the current status of air leakage post-intervention, reflecting a clear understanding of the building’s airtightness improvement.