Thanks!
We use the Rais stove for heating. Not the open fireplace. That hardly provides any heat at all.
We have an air handling unit which privides fresh and clean indoor air. It has a rotary heat exchanger which uses the warm air from the livingroom to warm up fresh air from outside, and distribute warm, clean air to other parts of the house. This actually works very well. The sollution is from Enervent, I believe a Finnish company. In one of the pictures (where you can see the left rear BL4000) there is a small spot underneath the roof, where the system takes out the heated air from the livingroom.