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It's most definitely not the goal to suffocate the inhabitants, no, and the goal also isn't to have the natural humidifiers living inside create a tropical climate ripe with microorganisms and stuff. Yes, you want to avoid excessive air exchange because you'd lose a lot of heat that way, but tightly sealing a house would be a very bad idead indeed. If you do make the outer envelope essentially airtight, that gives you very low energy consumption and is part of the passive house concept, but then you need active ventilation, which obviously implies a hole in the envelope, and thus will keep the pressure inside equalized with the pressure outside (modulo a small differential caused by the ventilation itself).