CFM question

im in the process of installing ventilation, i havent decided on a light yet, but the space is 24" wide by 15" deep and 70" tall. What CFM would i need for a 250, 400, or 600 respectivley.

the ambient room temp is around 70

i would like to know this as well.

thanks

A general rule of thumb is you need to change the air in the room once every 5 minutes. I have a 270 cfm can fan on my 2 600s and it keeps em icycold. you have a 13.5 cubic foot cab approx. in that small of a cab i would change the air every minute at least.