I’ve explored the sick building concern and it’s actually fairly positive. The goal is not to eliminate air changes with the outside but to funnel them through a single vent, extracting heat from the air before it’s expelled to the outside, transferring that heat to cold air brought in from the outside. It’s much more efficient than having the heat leak out of building all over the place. Further, the buildings get new heat from electrically powered heat pumps which are also more efficient, and have no carbon monoxide or carbon dioxide emissions within the building which are a risk factor.

The net is healthier air. But it is expensive to build buildings like this, is increasingly less relevant from a global warming perspective and may not address embodied carbon at all.

Germany is now at 46% of its electricity from renewables annually, so you are well down this path already.