Veg Room Ventilation

[StoneyMontana]

Hey guys, I am in the process of building my veg space which is rectangular, 6.5 ft long x 3.5 wide x 3.5 ft tall.
I am planning on running a 4 ft 8 lamp t5, and a 2ft 4 lamp t5 for lighting.
This space is a basement level under stair storage area so it is a comfortable temp all year.
I am trying to figure out if a 4" fan and filter will be sufficient in this small space with the t5's or if a 6" will be needed.
I have never grown in a space this confined, and I have never run t5's so I am hoping those with experience in t5's and knowledgeable on ventilation, can give me some good advice.
Every dollar counts in this build so I hate to waste the cash on a 6" fan if a 4" will suffice.
I plan to run a carbon filter as well on the exhaust that I should probably factor in.

 

[Vanilla Phoenix]

If you have a doubt about what size fan to use, I would go with the 6" and put it on a speedster to adjust the fan speed. I have a 3ft 4 bulb T5 in a 42"x24" closet but have 8' ceilings. I use a 4" fan with a speedster slowing the fan to around half the speed and temp at tops of plants are 3 degrees above temp coming into the 4" intakes.

 

[lotus710]

Ive never ever vented my veg room and never had any problemsXD and i cant ask for more if im getting the veg i want in a month or less i think the four inch fan will be perfectly fine even at 100cfm but active air has a 4inch at 165 or something

 

[Granger2]

Multiply it out. 80 cu ft. A 4" fan will give you about 170cfm. This is about right for 2 exchanges per minute for heat control. Good luck. -granger