1 powerful fan like mine is enough to get cool air from outside...
Your fan has an insane CFM. It sucks more than 7m³/minute through that 120x120 hole.Sadly I can't find it anywhere in Europe for normal price. Will do more research, though
Where did you get it and what did you pay?
im also from europe(norway) and i bought it on ebay for 50usd i think.
send the guy a message, he have more to sell but havnt put it on ebay.
here:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&_trksid=p4340.l2557&nma=true&rt=nc&item=130532184228&pt=LH_DefaultDomain_0&si=Am6nW0aTEz1k%252B58U9jfCoUVCZP4%253D&viewitem=&hash=item1e645310a4#ht_2215wt_905