Exhaust Fan Pulling Out Cold Air?!?!

[thehaunt]

Ok I have two side-by-side rooms that are 4x4 each approx 8-9 ft. celings. I am running a 8'' 740 cfm exhaust fan with passive intake. Now I have been battling a bit of higher temps that are staying 80 F or above, needs to be lower! Now, when I was up in the attic I noticed that the exhaust fan air is cold! WTF!?!? I assume its on too high or I need some intake, which I'm not sure if active fans are the answer because the exhaust fan pulls the door shut practically so I know its pulling air from somewhere. The ambient air outside the 2 rooms (all in the same bedroom, 2 grow rooms separated by poly) in 72-76. My problem is I cannot intake directly from outside so I will use a window ac in one of hoosierdaddy's boxes to cool the room outside the poly of those 2 rooms to generate cold fresh air. Even when I had the ac on and running, pulling intake to cool itself from the window, I noticed small openings pulling in hot outside air to the rest of the room I assume from the negaative pressure of the exhaust fan. I would like to run the window ac as the house ac isnt efficient to use for cooling that room at the same time as the house. What should be my solution? I have been thinking either fan speed controller, a 6'' intake fan split-ducting into each room (but from where?), or possibly both. I am very frustrated as I have read numerous times that you should overdo your exhaust which I believe I did somewhat. I need some help Farmers! thanks

 

[xX Kid Twist Xx]

a quick solution if you add co2 you'd be rocking with those temps. most poeple keep there rooms around 80-84 with co2

 

[Jalisco Kid]

If you have a/c and co2 why vent at all.
My attic is over 120* any air coming from my room would fell cold up there. JK
Have you tried to put a fan on your register to see if you can pull enough cold air out of your plentum to keep your room chilled enough?

 

[Tobor the 8th Man]

OK if you have the poly grow room in another room that you can a/c that is perfect. You a/c the room air. Then you have PASSIVE intake vents into the poly room. Use PVC pipes with bends or build a light proof intake floor under the poly room to draw the a/c room air.

You have an 8" exhaust fan so you need at least two 8" diameter PASSIVE intake holes. I would use three. Or how ever many smaller holes that would equal the same area size as 2-3 8" holes.

Now the fan will only draw in the cool a/c air because it can suck more than it can use from the passive intake holes.

If you don't have intake holes or try to use an intake fan (unless it is equal too the exhaust fan) the exhaust fan can out pull the intake and now it will draw in warm air if it can from some place other than the a/c'd room.

This keeps your a/c from having to cycle as much too. Because it can cool the bigger room and then that is like a cool air reservoir and takes longer to warm up and run the a/c again. The poly room will draw all the cool air it needs and it will stay much cooler.

 

[cheyenne]

If you have a/c and co2 why vent at all.
My attic is over 120* any air coming from my room would fell cold up there. JK
Have you tried to put a fan on your register to see if you can pull enough cold air out of your plentum to keep your room chilled enough?

Eggsactly. 80dg air coming out of your exhaust in a 100dg+ attic is going to feel cold...its all relative.
Get a Co2 tank and rock those 80dg temps....your girls will love it!

 

[thehaunt]

OK if you have the poly grow room in another room that you can a/c that is perfect. You a/c the room air. Then you have PASSIVE intake vents into the poly room. Use PVC pipes with bends or build a light proof intake floor under the poly room to draw the a/c room air.

You have an 8" exhaust fan so you need at least two 8" diameter PASSIVE intake holes. I would use three. Or how ever many smaller holes that would equal the same area size as 2-3 8" holes.

Now the fan will only draw in the cool a/c air because it can suck more than it can use from the passive intake holes.

If you don't have intake holes or try to use an intake fan (unless it is equal too the exhaust fan) the exhaust fan can out pull the intake and now it will draw in warm air if it can from some place other than the a/c'd room.

This keeps your a/c from having to cycle as much too. Because it can cool the bigger room and then that is like a cool air reservoir and takes longer to warm up and run the a/c again. The poly room will draw all the cool air it needs and it will stay much cooler.

Boom! Now I have a great plan of attack. Why pvc pipes out of curiosity? Could I use 8'' insulated ducting? Thanks everyone for the quick help. Thats what will make me want to be on here more.
JK, no I hadn't even thought of adding a fan to the register. How will that affect the rest of the house air? thanks again for the help guys and hope you all can help me get this room situated perfectly.
to those who said co2, no worries, want to get this room and my strains dialed before I add that. Think it would be somewhat of a waste. it would be my first time with it at well so want to make sure other factors are 100% in check.

 

[thehaunt]

Tabor, also meant to ask how you would go about building a "light proof intake floor under the poly room"? weighing out my options on how to do this.

 

[Tobor the 8th Man]

The PVC is easy to make a light block with elbows. You paint the elbows flat black on the INSIDE. Then put one on the outside the tent end of a short pipe and one on the inside end of the pipe. The light can't bend and it can't be reflected around the corners.

A light proof intake floor is simple if you saw a picture but probably difficult to explain.

There are a couple ways I know of. i will just make up dimensions but you can make it any size.

Say you have a 4x4 piece of plywood. get four 3 foot pieces of 2 inch x 2 inch wood strips. Make a square with them so they are centered on the plywood. Now keep the top and bottom ones where they are but move the side ones out about 4 inches so now the 4 pieces of 2x2 no longer meet at the corners. There is a good gap. Now glue or nail the pieces in place.

Then take 4 pieces of 2x2 about a foot long and place them on the outside corners across the gaps but not touching the other wood strips and fasten them.

Now drill a bunch of 2", 3" or 4" holes in the plywood in the area your wood strips make. Then put the stip side of the plywood down. Now air can find it's way into the box through the gap in the wood strips and up through the holes. But light can't make the bends the strips creat.

I hope this pic helps. Move the corner pieces out farther so lots of air can pass through. You could even use 4' x 4" boards if you need more floor support and more air flow. The floor would be 4 inches off the ground with 4x4 and more air can get in. But 2x2 will let in a lot of air too.

 

[thehaunt]

I run flood and drain tables over a big rez so I'm going to go with the pvc pipe option as my passive intake. I appreciate your help and once I get that done will let you know how things are going and if temp is in check.