at great and admitted risk of being shown my error i will try using Lee's comments and some things i THINK i gleaned from some of member nortcan's comments to make another explanation.
i live in a little house. there is a uninsulated block basement of 680s.f., a ( currently, about to be remedied )partly insulated 1st floor of 680 s.f. which is where my stove is, and there is an uninsulated 2nd floor ( we don't care how much or little heat gets up there, we like to sleep cool. there is minimal insulation in the attic.
i think the neutral stack plain here is about 5 ft up the 9 ft. 1st floor walls. that is also the centerline of the thimble into my chimney. this shows me why tightening up my house much more is so important.
the neutral plain runs right thru the vertical center of 4 of my worst fitting windows (so it's pushing air out the top of them and pulling it in the bottom, again about to be remedied ) the plain is also responsible for pulling cold air up out of the basement and in from the front enclosed but unheated front porch under the doors ( mostly fixed with a draft dodger )
the plain is also responsible for forcing air out of the house everywhere it can on the second floor.
how can this be dealt with ? well, nortcan has made very good points to the effect that we must 1st, achieve a very tight and well insulated envelope to start with. ( i'm working on this with great determination ) only then can we control the effect of the stack plain.
if we start from that point we can add an air handler that will allow us to precisely control the rate and location that air comes in and leaves the house for ventilation purposes. it will also free us from drafts and concerns over combustion air access in all but constant limited draft conditions.
there you go, i've got my body armor on so blast away.