I joined the 4 ring club today with the tightness in a duct system.
848 sf apartment. 15 CFM at 25 leakage to the outside. They still have to seal the attic plane and a few other places. I will be back for finals on this one. The HVAC got it right on this phase of duplexes. 18 months ago we had some leakage to the outside in 150 CFM at 25 range. One unit had 120% of system air flow leakage total.
Any one else have a 4 ring success story.