ventilation

This should help ya out https://www.rollitup.org/view.php?pg=faq&cmd=category&id=67

The exhaust is up high small hole poweful fan sucking the hot stale air out. The intake has no fan making it passive. For me I like to make it about twice the size of the exhaust. If you wanna do something cool. You can take a drill and drill large holes to act as your passive intake. Do this in a side by side pattern. This will make you passive intake. I did this on my last set up. Measured about 4 inches tall and 12 inches long. The exhaust pulled the air via the top causing sort of a vacuum that pulls cool fresh air in through your intake.

thanks for clearing that up. I was thinking of getting a centrifugal blower 3 speeds 1000cfm on low but not sure if duct work out is big enough to handle it. I have a 3" exaust that steps down to a 2" before leaving the house..

Go with the biggest you can (taking noise and other factors into consideration). The better the air circulation the happier the plant.

If you are concerned about heat, you may want to think about getting a stronger exhaust fan. Depending on your setup, you might get more air movement with one strong fan (can fan, etc.) vs. a couple of desk fans. You also would merely have to widen your existing intake hole (as opposed to widening it and cutting another). Definately follow Mogie's advice.

Also, if you are using a HID light, you may want to consider air cooling (glass, 6"-or-so ducting, and one or two in-line fans). That was the only way I finally got temps down.

Try to duct air in from a room that is air conditioned for better cooling. Also, running your lights during the dark hours will help keep things cool.

When dealing with fans, the noise level is measured in sones and the lower the value the quieter the fan is. 1000cfm is a lot of air movement for a 100cf room. Stepping the duct work down will make for more noise as the air pressure increases as it passes through smaller and smaller duct work. Of course this might not be an issue for you depending on your situation.

With an active exhaust and a passive intake, the exhaust lowers the air pressure in the room. With a lower air pressure, air will rush in through the opening to a room with a higher air pressure. This forms a vacuum of sorts. If you have an active intake and active exhaust of the same specs, the air pressure in the room remains basically constant and can allow odors to leak out. I noticed this after installing an active intake. I have since move the second fan to an exhaust and immediately noticed an overall improvement in temp control and odor control.

Good luck!