Lesson learned: It appears the mechanical work, conducted after air sealing, may have introduced significant air leakage. We have yet to have energy auditors return to find out if this was the case, or whether there is another explanation for the following: An initial a 2-door blower door test (1 door on each unit of the duplex to equalize pressure) showed 503 ACH50 for the unit to be renovated. During air-sealing, a one-door blower door test showed a reduction from 850 to 739 ACH50 for the duplex. As only the one unit was air sealed, one would expect the 111 reduction would apply only to that unit, resulting in 392 ACH50. However, a 2-door test performed after mechanical work showed 640 CFM50. (No sleuthing for location of air leakage was done at the time, for reasons too complicated to explain.) That last number is listed below, even though there is still an element of doubt.