Airtight isn't really the best way to describe it. Rather it's controlled air exchange, this way instead of 1000 tiny leaks all over you have a central controlled means to exchange air.
Passive home typically have ERVs or HRVs (Energy/Heat Recovery Ventilators) to achieve this, they can control the heat/humidity in the air.
So did you have gas at some point before? Due to some moves over the last year and a half I've been able to use resistive, induction, and gas in a relatively close time span. I've found both quality gas and induction cook tops are fantastic and I could happily live with either. I did have some annoyances with gas (smell, maintenance, risk with small children), nothing that couldn't be worked around but given the performance equity with induction I find myself preferring it instead of gas. Curious what drove you the other direction.
Most passive houses I've seen have windows that open, but they are typically double/triple glazed (depending on climate) and are casement style instead of the more typical (and inefficient) double hung. They also typically feature a ventilation system to manage air movement precisely to prevent the issues you're concerned about.