exhaust & intake fans

I'm building a new grow space in the basement 6 x7 feet. I am planning to pull air in from the roof and exhaust to the roof too through what used to be the chimney space. The house is one story above the basement with 6' attic space, so I'm looking at about 15 to 18 feet from the basement. I guess I need two inline fans, but what size to push and pull that distance? Do I need booster fans too?
Quote

get one max fan might be a little over kill but with that distance traveled you can get away with just one fan instead of two

The air on the roof is hot. Pulling fresh air from the roof kinda sucks (I know because that's what I'm doing right now). Also make sure your intake and exhaust are seperated by several feet.

I am of the opinion that you should oversize your exhaust fan by quite a bit. I have a large 8" exhaust fan that runs at "idle" (250cfm) during normal operation, but it kicks up to full speed (700cfm) if my room temps get too high. This instantly cools my room on demand. My fan is controlled by this: http://aeroponicsnmore.com/climate-control-ventilation-c-23_5/temp-2v-fan-speed-control-variable-idle-setpoint-p-181 It sure beats spending $500 on an AC.

So the 8" fan exhausts all the way to the roof? Do you use an 8" to pull air from the roof too? You pull the air from outside, not from the attic, right? I didn't think about the air being hot above the roof.

sarita99 said:

So the 8" fan exhausts all the way to the roof? Do you use an 8" to pull air from the roof too? You pull the air from outside, not from the attic, right? I didn't think about the air being hot above the roof.

Click to expand...

I use the 8" from the filter to the roof. I use a 6" HO (on a dial speed controller) for my intake on the other side of the roof. That way I can turn it up or down depending on how warm the roof air is. When I turn it all the way off, air from my house gets pulled in to the tent. That's not bad at all on a nice day! Yes, I'm pulling air from my roof vent (not the attic).

Seperately, I have my light hoods hooked up to another 6". That fan turns off when the lights go out or if the room is below 70 degrees.

This is very helpful, thanks. One last question: how many floors or feet away from the roof is your tent?

It's only one story house. But the vent is on the other side of the house. I have approx 50ft of hose for the exhaust and another 50ft for intake, up in the attic. Plus another 10ft+ looping around the inside of the garage!