Passivhaus is not focused on one metric. To achieve passivhaus there are many metrics measured. Energy use, overheating, air quality, thermal bridging... The list goes on. I'm not sure what one metric you're referring to.
Passivhaus does not mandate plastic based insulation. Many are built with cellulose, wood fibre,straw bales...
They are not in any way more prone to water intrusion any more than any other building.
They are far less likely to suffer sick building syndrome because ventilation standards are far higher than for 'normal' houses.
You can open the windows if you want. Sure, if you do it in -10 temperatures you lose some heat.
Passivhaus 'nutters' are generally apathetic about PV. You don't need PV ; simplicity is part of the point. The marginal cost on insulation is generally pretty low. The difficult but it's getting builders diligent enough for the challenge.
Hope that helps to encourage you to continue researching the subject.
So, I presume that in the case of a fire, they go up like a match?
Where is your sacred R value now?
The PassivHaus stuff is a really good example of the derangement you get when people try to optimize for only one metric. PassivHaus's are expensive, mandate the use of petroleum based insulation (you're living in a plastic burger box), prone to water intrusion mold and sick building syndrome and the supposed efficiency gains disappear when you open a window.
Telling is the PassivHaus nutters response to builders wanting to use solar panels to build houses with low external energy needs. AKA why spend $100k on insulation when you can put a $20k worth of solar on the roof and a ground sourced heat pump. PassivHaus response is to get regulators to ban that option.