Proper ventilation for 70 cubic foot grow room?

Hey,

I've got grow room of 70 cubic feet/2 cubic meters, I'll use a 400w hps, I'll put 7 Lowryder #2's... How many times the air in the room should be exchanged? In other words, how much should be the CFM(cubic foot per minute) of the fan/fans?

I read from the FAQ that the room volume should be exchanged 3-5 times with above average temperatures, is this the case for 400w hps?
Or maybe someone has grown here with 400w, if so, what kind of ventilation did you use?

I'm trying to get along with minimal but proper amount of ventilation, as on a budget...

Or, how much less ventilation should I use if I would buy Cool Tube(though it's about 100usd)?

Thanks

clearing your room out 3-5 times a minute is ideal, but i have gone much lower and had no problems.

Razz is correct ,
Rhizome has a good thread somewhere on here that addresses this issue and many others inteligently w/ equations / facts . Image Reaper grows w/ a 400 hps and might be a lil help to you also .

I'd use a cooltube and pull the hot air from cabinet and light both through it and lotsa passive intake air , about 250 - 300 cfm would be nice as long as your not gonna try to use a scrubber w/ it too .

Peace
Crispi :jointsmile:

I had a similar sized room...I used a 250m3/hr fan, worked really well with a duct going out the roof...don't know what that converts to in cfm sorry