OK, although "stupid Germans keep opening windows to defeat stupid green goals" is of course a take, in reality, a modern energy-efficient Euro-style building w

OK, although "stupid Germans keep opening windows to defeat stupid green goals" is of course a take, in reality, a modern energy-efficient Euro-style building will: -Indeed be 'airtight', in the sense that limited air (and noise, as a bonus) will enter or leave the building except via defined ventilation routes. -Offer primary 24/7 ventilation (mostly for CO2 management) via ingress/egress vents as part of a balanced ventilation system, which performs 'comfort' regulation of incoming air temperature using heat recovered from outgoing air. -Heat or cool the building via under-floor convection connected to a reversible heat pump. This will slowly but surely bring most of the building mass to a comfortable temperature regardless of season. -In addition to basic ventilation and heating/cooling offer very-well-insulated yet securely operable windows for additional temporary ventilation. Window openings are very much defined ventilation routes as part of the 'airtight' plan. The important things to keep in mind here are that the balanced ventilation system prevents things like mold already, and that opening windows for brief periods of time (as in: measured in hours) for (perceived) comfort won't impact energy efficiency very much at all. The most relevant criticism here is that retrofitting existing buildings for the above scheme is a significant challenge, but that doesn't quite seem to be the point the article wants to be making...