A radon ventilation should not go through other vents, it should have its own pipes. Lay out drainage pipes, 4 pieces, in a star shape about 1 meter from the foundation wall towards a midpoint and then a 110 pipe straight out into the fresh air. If that pipe goes indoors, you will get natural draft, and if needed, you can install a fan later. Make a sliding joint on the pipe so it can be opened; there are small fans that can be mounted in a 110 pipe and controlled with a motor dimmer. The negative pressure should be about 0.1 - 0.2 bar to avoid drawing cold air into the foundation.