I once had 40-50 GPUs in one room. I had an open tent over the GPUs and fans above that sucked out the air and then tubes went outside and up into the air 5 feet. Next I also had fans that pumped air into the room in front of all the GPUs and box fans that blew over them. I used a box outside that had an open bottom and open side. It was bigger than the window and mounted against window. I found out this prevented rain water from getting in and could leave fans on during a rainstorm. The type of fan you use is important. For input the standard box type fan will work. For output use only inline fans as they can create more pressure but use more watts. 12 inch ones work great or 6 or 8 inch too. If you get the smaller ones you will need more, but that can better pull air from different parts of the rigs too. I put a blanket over the top to quiet it down. It will actually work without intake, but you will create extreme negative pressure in your house which probably isn't healthy to live in. You need to measure exhaust temp as if its too high, then you need more exhaust.
Eventually I switched to a 10x12 shed and used the same design. Air in one side and out the other. I put in the biggest windows, then removed them. I had it designed so on the long sides were both windows and no where else. Next, I removed the windows and mounted a huge overhanging box 40x50x30 inches with two open sides and placed bug filter under it and stapled it to the wood. I has to vacuum this weekly. It was drilled right into the shed where wood studs were for windows. I mounted a two 2500cfm fans on input on inside window seal which was extended with wood and had (10) 6" inline metal fans on output as I had used these inside the house. I even had space to add two more 12" inline fans on output too and bought them, but never installed as it wasn't needed even at 100 degrees Farenheit. This ran 70 GPUs for a year, but did run them at 70% power and keep fans running 95% if temp went over 62 Celsius. Noise wasn't an issue as the shed deadened a lot if it. I did have to paint the roof white as it was overheating until I did this. I didn't need to insulate it after I painted the roof white. Cost of shed was $4200 delivered. As far as wiring, it ran off 240v (2 wires only) I used two 4AWG wires off two 60A breakers that ran in a sealed and glued PVC pipe for 90 feet to the shed wiring connections, which was over-sized on all connections. I also used the feel method on wiring connections to make sure my breakers were never even warm. Never had any fires, etc. Never used lightning protection and had three motherboards fry. No GPUs were effected. I had one fry the CPUs and memory too. Two motherboards NICs quit working, so I replaced them with USBs ethernet ports and worked perfectly. Lightning can be expensive.