Now that you mention it, there does appear to be an air exchange between the living space and the attic space via the furnace closet so this can't be a correct setup that in addition to both of the air sources being located at the bottom of the space. Good point. Thanks. I can't wait to hear what the city has to say about this. I have no interest in doing any kind of calculations or get into a pissing match with a builder but the setup didn't look right so I questioned it and now we keep going back and forth and for the sake of my clients I just want to get the question resolved.