Well my gear is sitting on the roof (build a nice 30m² mine up there )
The only way of getting air out is drilling a hole through the roof and embed a plastic pipe.
Usual pipe size is 125mm or 150mm diameter.
There are so called In-Line Fans to put directly into the pipe (clean and easy) but my fear is that they aren´t able to pull enough air. So I need a radial vent probably and connect it with a flex pipe to the roof pipe
Fresh / cold air is coming from down the house since I will leave a grid to the 1st floor.
Maybe someone here did this already or has the straight tip for me