Yes I understand the confusion and I think this will clear the haze. The neutral pressure plane is the point in the house where pressure outside equals pressure inside. Below the plane is negative pressure relative to pressure outside and above the plane is higher pressure relative to pressure outside. This it how it moves because it's relative to pressure outside! I'm all wound up now hahaha
Where's Fred? Please pardon my enthusiasm.
I can see where (and have previously mentioned that) the reduction in pressure in a basement due to the chimney causes more inward infiltration due to the higher pressure outside rushing inward to fill the void. But once again its increased pressure rushing toward the direction of reduced pressure, and things like books that claim it to be so can never reverse this fundamental law of entropy. If outside pressure is rushing in, then inside pressure from above must simultaneously be rushing downward. Pressure must move from high to low. it matters little if the pressure is from inside or from outside.
Unless things are different when the entire house (high pressure to low, upper regions to lower regions) is at a pressure level that is below that of the outside air. Hmmm???
But for that case would the chimney draft, or would it backdraft? Double-Hmmmm???
The bottom line though is still: What relevance does this have to answering the question of which causes more coal to be consumed. The baro damper, or the MPD, or neither of them?