I am writing this review for two reasons. The first reason is the Cloudline T4 fan unit itself, and AC Infinity's awesome customer service. The second reason is the title of the review. I am not using this in a grow room, but in an encapsulated crawl space as an exhaust fan.This fan is outstanding. It was easy to install and setup. For my use, I just have it strapped to a short cinder block and sitting on the floor of my crawl space. I have a Vivosun duct cover over the intake, as the intake is not connected to anything, and I didn't need a carbon filter for my application. I then have the AC Infinity 8' ducting connected to the hard duct that exhausts to the outside.My Fantech FR-100 was pulling way too much air, causing too much negative pressure in my townhome, and causing too much noise, mainly from bad mounting and thus vibration noise. The FR-100 was literally shoved into the hard duct, sheet metal screwed on, and then duct taped. Basically, just hanging there off of the hard metal duct.Anyway, I was wanting to know the CFM ratings per fan speed settings, and AC Infinity support was awesome, quick, friendly, and got me that information fast through their chat.The other issue I had, was the FR-100 was way too close to the inside floor intake vent, about 5' away. This made for uneven temps in my crawl space due to lack of air circulation. Air pulled into the crawl space and exhausted right out. With the T4 and ducting, I was able to place the fan much further from the intake making air circulation better and thus I now have more even crawl space temps.My crawl space is small, about 250 ft, and per code, only needs about 5 CFM. Setting 1 is about 45 CFM, and I am currently set on level 4, about 100 CFM. This in part due to the dust cover lowering the actual CFM and a backflow air valve on the intake from the house. I need to create enough pressure to make sure the valve opens and I was testing a few things. I will like lower the level to 2 eventually.Anyway, this Cloudline T4 fan, is truly whisper quiet. At 10, I am sure there is some noise, but in testing up close, from levels 1 to 6, you could barely hear it at 4 - 6.Overall, I am super impressed with the Cloudline T4 and its smart controller (which I will be upgrading to the WiFi model).
