Here is my highland cooling setup (excuse the clean room!)
There is currently a 5" 65 CFM computer fan in the window mounted to a "duct collar" (flat piece of metal with a 5" hole in it) the collar is mounted to a flexible aluminum duct allowing the air from outside through the 4" flexible aluminum dryer vent duct to the plant shelf. Right now the window is only open a little bit. When the temps are too cold I shut the window and the air at the surface of the window is cold enough to bring the temps down.
At each taped area is a duct "T" which allows some of the cool air to empty out onto one of the three shelves where the plants grow. The top of the duct is an " L" which empties the last of the fresh air, also it get's the most fresh air so despite physics/thermal dynamics/whatever the top shelf is actually the coldest! lol
Currently I only have a few CPs in some covered tubs on shelf #2 the rest are succulents but when I switch the top two shelves over to HL plants next spring I will simply glue a 2" diameter hose into the output hole of an ultrasonic humidifier from the pharmacy and cut a hole in the air duct and place the humidifiers output hose into the duct so I'll have cool wet air blowing into the shelf. This is how I cooled & humidified my HL Neps when I grew them before. It's very easy to do this cooling project if you live where it gets cold enough.
People in the south can do the same but instead of pulling air from outside which could be too warm place a "wide vent" output on the rear end/window side of the PC fan and place the wide vent potion over the output of a 10,000 BTU window A/C unit. This costs a lot to run (I did this for HL Neps from mid June-mid Sept) but you'll get your cool temps.