Fans

Mat, Noctua Industrial series is pretty good (Link to Noctua). With that space, you can probably go with NF-A14 (140mm), but you can run it at the lower speed/voltage. It is quiet. It's more expensive, but it is water resistant, and you can splash water to it. I've had those in my grow tents for 5-6 years. I used to run it for 24h, but I only turn them on when they aren't drying (most of the time no fan running), so actual run time is probably 3 years or so, though.

 

I'm just putting together up a new set up and need a better fan system so the timing of this post was great.

 

My 2¢ worth is go with more of the ~5" (120mm) axial type (computer type?) fans. You can get really high volume air movement with them if you pay attention to that (mine are 113cfm each) and they seem to last just about forever for me. I just put two of them in my new cool case which were in my wardian cases for several years, and then my growrooms for 4-5 more years, then sat in the basement for another 15 years since I built the greenhouse, and they're doing just fine. Needed a couple more so ordered off Amazon. Cheap! But pay atttention to the wattage. The 12 amp ones aren't really worth bothering with (and need transformers); I got the standard 120W household current ones). And to the type of connector/cord. My cords connect to the fan's two-pin male fitting and then have a standard house lamp type plug at th other end.