I had a blower door test and not suprisingly my 110 yrs old house was a
leaker. So after covering the house in foamboard , [ finished with OSB
and cedar shakes] new windiws and I sealed everything . I found it
was so tight my furnace chimney wouldnt draw , it spilled in . I
replaced apliances to forced venting. If your chimney draws with
your vent fans and dryer on you will be ok. Mine would not draw with
nothing on. Only newer homes have been built real tight, Tyvec etc.