well ill stick to the 150 fan as its like 200m3+ roughly and only £5 more so makes sense tbh
IF thats what you decide.
If someone comes to me for help i help them as best i can but there are certain rules to follow when designing a grow room.
These rules are specified by the type of system you wish to run.
1 major rule is that you pull air and exhaust air in 2 different places. This is basic grow room design. IF you have a Hydro Shop near you i suggest you go there and look for the URBAN GARDEN MAGAZINE with the orange cover on how to design a grow room.
If you plan on leaving a window open then you need to exhaust away from your grow room its as simple as that. Now this could simply be a hole in the ceiling of your room going up into the attic. OR it could be a vent on the window allowing hot air out.
But one thing that remains constant is that if you are using passive or powered intakes is that you take your clean air from an area that is not getting consistantly warmer.
Your bedroom would become unbareable after a few hours of running your system even with the window open.
Something else you also have to plan for is running during the summer months. And with your current idea your temps inside your cab would be too high if you are still exhausting into your bedroom.
J