I'm currently renovating a house in The Netherlands, we're installing a heat pump and to make the place more efficient we also replaced the glass with triple glazed (but without vents in the frames as they let heat escape). Given that we were effectively making our house a "sealed envelope" we had to add mechanical ventilation (ERV) to ensure proper airflow around the property. As you can imagine, retrofitting ducting around an old house required a LOT of creative work!