6x6 walk in closet ventilation

[Being As An Ocean]

Ok guys I rent my house and would like to keep this grow as non invasive as I can which means I don't want to punch holes into the walls. The good news is that the closet itself is 6'x6'x8' and has a 2'x1' direct access point to the attic with it's own outtake practically already set up directly out the roof before I even touch anything. The problem is making sure the closet receives enough fresh air for the plants and keeping it cooled during summer.

My original plan for intake was to replace the door with my own make shift door that I can cut a hole into the bottom for an intake and just use a 250cfm fan and draw from the room the closet is in. With a 450cfm exhaust fan, will the 250cfm intake allow enough fresh air for the plants? Second problem is temps - If I have the room (not closet) cooled with AC, will this intake provide enough cool air to keep the closet in the right temps during summer?

In case it matters my outtake would be set up like this. Carbon filter > Cooltube > Fan > Ducting out the roof.

 

[bazookajoe]

id use a speed controller on the exh fan to slow it down a bit and a window unit ac In the room the closet is in just to make sure you have adequate cooling when your central air kicks off. what lights are you planning on using? id also use your door plan for the exh vent to the attic as well.

 

[Being As An Ocean]

id use a speed controller on the exh fan to slow it down a bit and a window unit ac In the room the closet is in just to make sure you have adequate cooling when your central air kicks off. what lights are you planning on using? id also use your door plan for the exh vent to the attic as well.

The exhaust fan already has a speed controller. I still would like negative pressure in the closet though, but obviously not too much. I thought about having a closed line with the cooltube but just seems unnecessary if I can keep temps down, right?

I don't have central AC, only heat. Window AC was the primary idea although I was wondering if that would be enough with my intake plan instead of having to buy a portable AC for the closet itself.

I'm running a 600w HID setup so I can't utilize the whole 6x6 anyways (at least with the 1 light setup.) I was also thinking earlier today about busting out my old 4x4 tent and try to stick it in there, it would be cramped but allow for more controlled air flow to the plants (though not sure how that would affect heat.)

As for the attic the way it's set up is a board cut to size drops down from the top and it rests almost flush to the ceiling. Was going to just size up a 2nd board so that I can cut my holes without having to replace/repaint the original. Plan 2 was to just tape some insulating foam board to the ceiling with my holes cut.

 

[bazookajoe]

The exhaust fan already has a speed controller. I still would like negative pressure in the closet though, but obviously not too much. I thought about having a closed line with the cooltube but just seems unnecessary if I can keep temps down, right?

I don't have central AC, only heat. Window AC was the primary idea although I was wondering if that would be enough with my intake plan instead of having to buy a portable AC for the closet itself.

I'm running a 600w HID setup so I can't utilize the whole 6x6 anyways (at least with the 1 light setup.) I was also thinking earlier today about busting out my old 4x4 tent and try to stick it in there, it would be cramped but allow for more controlled air flow to the plants (though not sure how that would affect heat.)

As for the attic the way it's set up is a board cut to size drops down from the top and it rests almost flush to the ceiling. Was going to just size up a 2nd board so that I can cut my holes without having to replace/repaint the original. Plan 2 was to just tape some insulating foam board to the ceiling with my holes cut.

as long as youre sucking more air out then whats being sucked in youll have neg pressure. how many btus is your window ac, and sq ft. of your house? you wouldn't need much to cool a single 600w setup but if youre cooling your entire house with it plus a grow setup it may require a bigger unit or another unit. it doesn't take much cfm to remove heat from 1 600, but that alone wont keep your temps in check, unless your house stays really cool constantly. if youre pulling cooler air into the tent itll drop your high temps. but your tent air will never be cooler the the ambient air that's being passively sucked in.
I needed 65 degrees coming in to keep my diy box to keep it under 80 degrees with 1 600. I had to cut a hole in my central ac supply line to give me that 65 degree air, but that's when it was 90-105 outside.
you might want to combine plans 1 and 2 for the exh into attic, just for reassurance tape the insulating foam to your access board you cut.

 

[Being As An Ocean]

as long as youre sucking more air out then whats being sucked in youll have neg pressure. how many btus is your window ac, and sq ft. of your house? you wouldn't need much to cool a single 600w setup but if youre cooling your entire house with it plus a grow setup it may require a bigger unit or another unit. it doesn't take much cfm to remove heat from 1 600, but that alone wont keep your temps in check, unless your house stays really cool constantly. if youre pulling cooler air into the tent itll drop your high temps. but your tent air will never be cooler the the ambient air that's being passively sucked in.
I needed 65 degrees coming in to keep my diy box to keep it under 80 degrees with 1 600. I had to cut a hole in my central ac supply line to give me that 65 degree air, but that's when it was 90-105 outside.
you might want to combine plans 1 and 2 for the exh into attic, just for reassurance tape the insulating foam to your access board you cut.

I feel like this is getting sidetracked lol.

Definitely would only cool the single room with AC. The problem is making sure fresh cold air consistently and effectively enters the closet. In winter my ambient room temps are around 67° so I wouldn't need an AC at all. (thermostat sits at 68° but the room gets colder than the living room where the sensors are.) Summer is the only concern for temps where it gets to high 80s but that's what the AC will be for.

The real problem I'm seeing is whether my intake would be efficient enough for the closet if ambient temps in the room stay around 68°-70°? I'm talking about a simple 250cfm 6" duct fan here. (with some neg pressure)

The last op I had a few years ago was setup in 2x5x8 closet with a single 600w using a passive intake. This was in a different house that had central AC at 72° and I never got over 80°. This is where I'm lacking proper experience and knowledge since I've only used passive intake from a small neg pressure setup.

btw for future reference Room = the bedroom the closet is in. Closet = the grow space. so we don't get mixed up.

 

[McStrats]

For that size space you only need a passive intake (no fan). A 4" centrifugal fan will give the requisite ACH, plus it will pull through a passive intake.

 

[Being As An Ocean]

For that size space you only need a passive intake (no fan). A 4" centrifugal fan will give the requisite ACH, plus it will pull through a passive intake.

I can't have a passive intake.. It would require me to have a big enough hole somewhere to get enough passive inflow. A 6" hole wouldn't be enough and would cause problems with my fan. I'm very limited to where I can place holes.

 

[McStrats]

I can't have a passive intake.. It would require me to have a big enough hole somewhere to get enough passive inflow. A 6" hole wouldn't be enough and would cause problems with my fan. I'm very limited to where I can place holes.

You mentioned a makeshift door with a hole in your opening post?

I work in industrial ventilation. a 4" intake and exhaust are more than adequate. Just chiming in to offer some advice as I do this stuff for a living.

 

[Being As An Ocean]

You mentioned a makeshift door with a hole in your opening post?

I work in industrial ventilation. a 4" intake and exhaust are more than adequate. Just chiming in to offer some advice as I do this stuff for a living.

I understand but I already have this equipment. I'm really only trying to ask about the intake and whether or not the 250cfm dust booster fan would be enough intake or not with the setup I've described.

Are you saying that I should set the duct booster aside and buy a 4" inline for intake?

 

[McStrats]

I understand but I already have this equipment. I'm really only trying to ask about the intake and whether or not the 250cfm dust booster fan would be enough intake or not with the setup I've described.

Are you saying that I should set the duct booster aside and buy a 4" inline for intake?

I didn't see the part where you said you had the 6" 250 cfm fan.

For a 6'x6'x8' space:

CFM(250) x 60 / volume(280) = 52 ach (air changes per hr) - you need around 15-20 ach. Get a fan controller and run it on 1/2 setting. Put the fan on the exhaust side but you need "make-up air". A passive inlet would be ideal as air exchange is crucial.

 

[Being As An Ocean]

I didn't see the part where you said you had the 6" 250 cfm fan.

For a 6'x6'x8' space:

CFM(250) x 60 / volume(280) = 52 ach (air changes per hr) - you need around 15-20 ach. Get a fan controller and run it on 1/2 setting. Put the fan on the exhaust side but you need "make-up air". A passive inlet would be ideal as air exchange is crucial.

YES! Now we're talking. Ok so let me explain.

By setting my 6" 450cfm inline as exhaust and the 6" 250cfm as intake, will that be sufficient enough exchange while not causing my exhaust fan to struggle by pulling too much neg pressure or do I need a different intake fan. Exhaust is pulling through a carbon filter so deduct 20% to be safe, that leaves ~360cfm exhaust with controller for fine tweaks. Again I can't have passive intake because it would need to be ~12" hole with my exhaust.

I guess I'm having a real hard time trying to explain this simple question, I don't know lol. All my past experiences have been with passive intake, but I can't have passive this time so I'm trying to find out how to properly set up an intake.

 

[chakup]

I'm still lost why you can't run passive? Just drop the fan out of the intake equation and you should be good.

 

[Being As An Ocean]

I'm still lost why you can't run passive? Just drop the fan out of the intake equation and you should be good.

First sentence to this thread,

Ok guys I rent my house and would like to keep this grow as non invasive as I can which means I don't want to punch holes into the walls.

The only place I can cut holes instead of through wall is through the doorway and the attic.

For a passive intake you need a hole large enough to allow enough air to pass so that you're not restricting your exhaust flow (and also ruining your fan.) I would need to cut a hole at least 13" in diameter if I lower my exhaust to exactly 288cfm needed for the closet.

1 hole = 13.2"
2 holes = 9.3" each
3 holes = 7.6" each

I don't have the space.

 

[bazookajoe]

My original plan for intake was to replace the door with my own make shift door that I can cut a hole into the bottom for an intake.

I seen this and thought it was what you were going to do. Missed the fan size ? And got right into your temp issue. I don't see why the active intake wouldn't work. Run your exh fan about 3/4 speed and it should be just slightly higher cfm with filter than the intake fan. Some neg pressure but not to much.

 

[McStrats]

You only need 75 cfm for 15 ach in a 228 cu ft space. Not sure where you are getting the 13" for the intake either. If there is any kind of an opening for air to enter the space the exhaust fan will pull everything through....you also only need *one* fan. Too many cfm also pulls everything through the carbon too quickly to scrub out the odors. Dwell time is a very important factor with carbon filtration.

 

[Being As An Ocean]

I seen this and thought it was what you were going to do. Missed the fan size ? And got right into your temp issue. I don't see why the active intake wouldn't work. Run your exh fan about 3/4 speed and it should be just slightly higher cfm with filter than the intake fan. Some neg pressure but not to much.

That is my plan. The fan size for 6" 250cfm is only because I already have it from previous setups. The whole point of this thread was to help properly set up an intake since I have 0 experience setting up a proper intake.

You only need 75 cfm for 15 ach in a 228 cu ft space. Not sure where you are getting the 13" for the intake either. If there is any kind of an opening for air to enter the space the exhaust fan will pull everything through....you also only need *one* fan. Too many cfm also pulls everything through the carbon too quickly to scrub out the odors. Dwell time is a very important factor with carbon filtration.

13" for passive intake only otherwise I'm reducing the efficiency of the exhaust allowing much less airflow and also killing the fan by trying to run passive air through something like 6".