Brian, aside from all the jargon, here is something that you have to realize, in our area. I have never seen a house (new or old) that had less than 15 ACH. No one, around here, air seals. A blower door is usually not needed. I just turn on the bathroom and stove vents and turn on the clothes dryer to air fluff and see many areas of infiltration. When there is no delta T (usually only for a month or two in spring and summer) I use a smoke pen and fogger. It does n’t take much to find air leaks when they are so many and when you are experienced with where to look, given the common building techniques in this area.
As I have stated, most customers don’t want an detailed, formal, quantitative audit. They want to know where the problems are, how to prioritize and fix them and where to find professionals who know how to fix them properly.
Also, many HVAC people around here are a joke and don’t know the proper way to install high efficiency furnaces (no combustion air intakes run). Doesn’t take a genius to call this out and save them 10% efficiency on the heating gas costs.
Hope this helps;