We moved into our new house with controlled residential ventilation without EWT at the beginning of December. It is now clear that we will retrofit it for the next winter. Regarding the window pane, for example, I was extremely surprised that at -10°C the panes outside are still covered with frost and ice flowers, but on the inside of the windows everything is almost room temperature. I had never experienced anything like that before. Moreover, we also have this Netatmo thing, in our bedroom we never reach these CO² values at night with 2 adults and sometimes 2 children.....those are more than unhealthy.....