We always love learning more about building science perspectives from Cindy Zeis!
I am sometimes asked (often in a challenging tone) the question "if all the ducts are in conditioned space, how can there be leakage to outside?" I get it, some versions of codes and programs say you don't have to test ducts if they're within the thermal boundary (codes) or conditioned space volume (standards) which could lead to interpreting all the air is staying inside. Of course, when running energy simulation models for a HERS Rating there is a penalty issued in the form of distribution system efficiency loss which is where folks can get a little testy. We sometimes forget there's this thing called the pressure boundary. A very important element to building design. My short answer on this is, the only way nothing could get out is if there is no infiltration (envelope) leakage aka breach of the pressure boundary and the whole HVAC system, including the air distribution system, is inside it. I have not yet found that home/building. Some are getting very close but most of our building inventory still has a way to go. For the longer answer, I'll refer to this article I wrote a while back. https://lnkd.in/e9Y6qZsV #MovingEnergyEfficiencyForward #PSD #HERSRater #RESNET #BuildingScience
