Insulated windows? That would apply equally to any other system. Where care is required is sealing around whatever passes through the window.

As to the negative pressure, personally I just leave the door to the room cracked open very slightly. But if you have central heat ducts air will get sucked in through that no problem.

What i mean is that if you don’t have somewhere to take the colder air to take from you just end up sucking hot air in.

In system where the pressure would be equalized the leaks would be much smaller. For some reason it's impossible to buy these type units in EU.